Improve on this combo - Forcecage + Cloudkill

[GiantOctopodes]

So for most targets, two high level spellcasters working in tandem to drop a Cloudkill and a Forcecage on a target during the surprise round is an automatic death. They get no reactions during the surprise round to do anything about it, they get no save to avoid being trapped in the Forcecage, and then once they're in it doesn't matter if they can save vs the Cloudkill every round - over the course of its 10 minute duration, or 100 rounds, it deals 500d8 damage, average 2250. It also works on more than one target, if they're close enough together.

Now, it's not an automatic kill vs spellcasters and supernatural creatures who can teleport, if they can make their charisma save to do so. Nor is it against targets which are immune to poison, or which have (between health and available healing) more than 560 HP, as well as both resist poison and a high enough con to automatically pass the save vs the Cloudkill. It would also utterly fail against someone or something capable of creating an antimagic field. Finally, though the Forcecage cannot be dispelled, the Cloudkill can.

That being said, if you have cause to believe that your target or targets do not have those capabilities, it's certainly a great start. If the duo cast from invisibility there's a relatively good chance of this working in most circumstances vs non spellcasters, and a decent chance of it working vs weaker spellcasters. My question / challenge to all of you, is the following:
1) What other capabilities would allow someone to escape from this trap, or survive it? Keep in mind the Cloudkill does damage even to creatures who can hold their breath and / or don't need to breathe, and though it normally moves every round, the Forcecage is a solid cube that prevents any matter or spells from passing through it, so the Cloudkill fog would be held in place. Furthermore not only can the Forcecage not be damaged by any means, it also cannot be dispelled via Dispel Magic.
2) What improvements could be made to this to cast a wider net and / or catch some of those "tough cases"? Assume you have 2 spellcasters of whatever class, capable of casting 8th level spells. I'm also open to non-magical possibilities. This already requires a great deal to work - them getting within 100 feet and getting a surprise round. Making it easier to execute or more guaranteed in that setup is ideal, adding additional complications or requiring them to get the target to a previously prepared location is not ideal.
3) With the same stipulations, what other combos or options exist to deal with some of those tough cases previously mentioned? Keep in mind that the goal is the guaranteed execution of the target, assuming concentration is not interrupted. Relying on a target failing a save, no matter how unlikely it is that they succeed, is not optimal at all.

I look forward to seeing what you come up with!

[meandean]

Sickening Radiance rather than Cloudkill:


Is only 4th level (so it's easier to create the combo, although admittedly this also makes it easier to dispel)
In all likelihood, no resistance applies
Kills after six failed CON saves

[J-H]

You can only do this once or twice, and then the DM starts using Forcecage on the party. It's really not a fun spell.

[Gignere]

You can only do this once or twice, and then the DM starts using Forcecage on the party. It's really not a fun spell.

It’s why you always prepare disintegrate at high levels.

[GiantOctopodes]

Sickening Radiance does indeed have a variety of benefits - it allows you to kill poison immune targets, potentially it's a much faster kill, and it doesn't obscure your vision of what's happening in there, on the contrary it reveals invisible targets, so it's much easier to confirm the kill. It also extends from a central point continually, so in a crowded environments everyone outside the Forcecage would not suffer ill effects, making it easier to avoid collateral damage than there is with Cloudkill. I think both are worth having in your toolkit, but I like that a lot!

Wall of Light is also a fine option, and does offer something unique in that it deals non-poison damage and deals damage on a successful save. It and Sickening Radiance have a significant overlap on what target pool you would use them against, and they are both fine options. I'm not sure what Wall of Force brings to the table. It's certainly cheaper than Forcecage, but it seems to serve the same purpose, albeit with a vulnerability to disintegrate effects, and without blocking teleport options which don't use the ethereal plane, and without actually blocking spell effects at all. Am I missing something which makes it a better option than it appears to be?

I definitely appreciate the replies, keep the great ideas coming!

Edit: Just as points of clarity, Disintegrate has no effect on a Forcecage, and Cloudkill can't move on from its position since it can't pass through the Forcecage, in case there was any confusion on those points.

[MaxWilson]

Mordenkainen's Faithful Hound + Wall of Force does the same thing, works on poison-immune targets, and comes online at level 9 instead of level 13. And you can do it multiple times per day instead of just in one or two encounters.

However, enemies with Dispel Magic or antimagic are not vulnerable to this threat.

[Sigreid]

My group did this with Force Wall and Sickening Radiance. It was hilariously brutal.

If you can trap your opponents in an area in any way, Sickening radiance will almost certainly kill them

[Yakk]

The idea that "the vapors cannot cross the field" means "they stop and stay there doing damage" is going to dissapoint you.

The vapors move away from you. If they cannot go further, they don't stand still. They go away.

[GiantOctopodes]

The idea that "the vapors cannot cross the field" means "they stop and stay there doing damage" is going to dissapoint you.

The vapors move away from you. If they cannot go further, they don't stand still. They go away.

Where on earth are you getting that? I mean you're free to run your game as you see fit, but that's not what the spell says at all. "It lasts for the duration or until strong wind disperses the fog, ending the spell." The fog not being able to move is not a strong wind dispersing it (just the opposite in fact). The 10' away from you part comes from "The fog moves 10 feet away from you at the start of each of your turns, rolling along the surface of the ground. The vapors, being heavier than air, sink to the lowest level of the land, even pouring down openings." Emphasis mine.

Setting aside a Force Cage for a moment, what do you think happens if it's just an airtight room the spell is cast in? What about if it's cast over a sewer grate, and the area it pours into (being heavier than normal air) is a contained one? In a 10' cube where it was captured, it is already at the lowest level of the land, and there's no strong wind. It has nowhere to go, so it doesn't move. And finally, a heavy wind is not present, and its duration is not up, so it lasts.

Mind you, you're welcome to play however you like. I just don't understand where that perspective is coming from, since it seems to be written like you think it works that way by RAW, when it does not. Note that RAW doesn't particularly matter here outside of academic interest, I'm the DM, not a player trying to pull off this combo. I'm trying to design a pair of NPC assassins, and am hoping folks will have ideas and suggestions. Most of my campaign is homebrew / houserules anyway, so trust me, I won't be disappointed in how Cloudkill works when my NPCs cast it :-)

We still haven't covered spellcasters really at all, which have so many ways of making problems it's absurd. A good portion of them without Subtle Spell could be shut down with a silence and a force cage, but that's simply delaying things. Without having a 3rd spellcaster in there (which is really too much), it's tough to think of how they would get off silence, force cage, And something like cloudkill or sickening radiance within a surprise round. I would rather not rely on a Simulacrum, as frankly I'm already doing other things with those in the world. For sorcerers who can cast dispel magic and so forth while silenced, I'm having a very hard time thinking of options which don't use magic items. Antimagic Sphere shuts them down mostly, sure, but what then? You could stick an antimagic sphere inside a wall of force and make a very formidable temporary prison, but what then? How are you actually killing them without being able to use magical effects yourself, in a way that's not just going at it with swords and hoping for the best?

[Galithar]

What makes you think that disintegrate doesn't work on a forcecage? The description of disintegrate clearly states it's interaction with creations of force, and force cage clearly state that it is "composed of magical force".

[MaxWilson]

We still haven't covered spellcasters really at all, which have so many ways of making problems it's absurd. A good portion of them without Subtle Spell could be shut down with a silence and a force cage, but that's simply delaying things. Without having a 3rd spellcaster in there (which is really too much), it's tough to think of how they would get off silence, force cage, And something like cloudkill or sickening radiance within a surprise round. I would rather not rely on a Simulacrum, as frankly I'm already doing other things with those in the world. For sorcerers who can cast dispel magic and so forth while silenced, I'm having a very hard time thinking of options which don't use magic items. Antimagic Sphere shuts them down mostly, sure, but what then? You could stick an antimagic sphere inside a wall of force and make a very formidable temporary prison, but what then? How are you actually killing them without being able to use magical effects yourself, in a way that's not just going at it with swords and hoping for the best?

There's always the good old "play dead" approach. If the target "takes damage" and "goes down", and a round later he's still not moving (let's say he made a successful Constitution (Deception) roll or something), how many sorcerers would be paranoid to keep baking the target for the full Cloudkill duration? Some of them, but surely not all of them. (And since they're apparently NPC spellcasters, let me put in a plug for giving NPCs psychological and emotional weaknesses such as impatience and arrogance in order to make the game and the gameworld more fun.)

[GiantOctopodes]

What makes you think that disintegrate doesn't work on a forcecage? The description of disintegrate clearly states it's interaction with creations of force, and force cage clearly state that it is "composed of magical force".

Mostly omission, the Wall of Force / Disintegrate interaction is specifically mentioned in both Disintegrate and Wall of Force. Wall of Force also doesn't indicate anything about blocking spell effects. Meanwhile Force Cage includes no such verbiage about interactions with Disintegrate, and instead includes verbiage indicating "and blocking any spells cast into or out from the area". Now, it's certainly valid to rule that the fact it's magical force, and blocking a spell effect just guarantees it gets hit by it, and disintegrate uses verbiage to say it destroys effects such as wall of force, not just wall of force itself. It doesn't really matter, as either way I'd want to stop spellcasters inside from being able to cast spells, and I don't see any advantages other than level and cost to using wall of force vs forcecage. But yeah rereading Disintegrate specifically there's definitely merit for the counterargument, my initial feeling on it was based on assuming there to be a reason for the omission of that verbiage in Forcecage.

Edit:

The problem is that per the RAW the center of effect for the spell moves away from you. The gas may stay in the area but once the center of effect is out of the Force Cage then the spell pops off in the Cage. You are relying on outside knowledge of fluid dynamics to keep the gas in the Cage but last I checked fluid dynamics is not a rule in the PHB.

Respectfully, once cast there is no center of effect, it conjures a cloud of fog, it's not a continual spell effect emission from a point like sickening radiance, for good and bad. The FOG moves 10' per round, not the center of a spell effect. Also even if the center of the spell effect Did move, as it could not move outside of the Force Cage, it would be stopped at its boundary, not poof out upon attempting to move through, just like a summoned creature or other contained magical effect.

Also, fluid dynamics Absolutely is a rule in the PHB, just like gravity, heat convection, and all other physics, which operate on the "same unless specified as different" principles. It's even referred to specifically in this spell! "Being heavier than air, the vapors sink to the lowest level of the land" refers to them operating in accordance with the principles of fluid dynamics. It makes no sense to claim fluid dynamics don't exist, as otherwise you also get rid of rivers, baths, and all meaningful interactions with liquids and gasses, if they don't operate in accordance with our normal expectations and have no other defined operational parameters.

[Galithar]

Mostly omission, the Wall of Force / Disintegrate interaction is specifically mentioned in both Disintegrate and Wall of Force. Wall of Force also doesn't indicate anything about blocking spell effects. Meanwhile Force Cage includes no such verbiage about interactions with Disintegrate, and instead includes verbiage indicating "and blocking any spells cast into or out from the area". Now, it's certainly valid to rule that the fact it's magical force, and blocking a spell effect just guarantees it gets hit by it, and disintegrate uses verbiage to say it destroys effects such as wall of force, not just wall of force itself. It doesn't really matter, as either way I'd want to stop spellcasters inside from being able to cast spells, and I don't see any advantages other than level and cost to using wall of force vs forcecage. But yeah rereading Disintegrate specifically there's definitely merit for the counterargument, my initial feeling on it was based on assuming there to be a reason for the omission of that verbiage in Forcecage.

Wall of Force calls out it's interaction because it is an exception to the norm. As disintegrate can only destroy a "10-foot cube portion of it". Wall of Force overrides this to "destorys the wall instantly" not a section, the entire wall.

I think disintegrate definitely needs to counter forcecage from a balance standpoint as well. That's the one real weakness to force spells, that disintegrate can tear a hole in them with no need to dispel and have an ability check against it. Edit: And not even having the option to attempt it means that it's still more difficult to get rid of than most other spells that could trap you.

I can see your point of wanting Forcecage to have something to make it special compared to Wall of Force due to spell level differences. The Charisma check to teleport out is a pretty powerful one, but it is still relatively easy to break out so long as they have multiple attempts and/or a decent Cha save.

[Gignere]

Wall of Force calls out it's interaction because it is an exception to the norm. As disintegrate can only destroy a "10-foot cube portion of it". Wall of Force overrides this to "destorys the wall instantly" not a section, the entire wall.

I think disintegrate definitely needs to counter forcecage from a balance standpoint as well. That's the one real weakness to force spells, that disintegrate can tear a hole in them with no need to dispel and have an ability check against it. Edit: And not even having the option to attempt it means that it's still more difficult to get rid of than most other spells that could trap you.

I can see your point of wanting Forcecage to have something to make it special compared to Wall of Force due to spell level differences. The Charisma check to teleport out is a pretty powerful one, but it is still relatively easy to break out so long as they have multiple attempts and/or a decent Cha save.

RAW disintegrate works against any creation of force. By a straight reading it should work against forcecage, tiny hut, etc... Although none of these are explicitly listed.

[GiantOctopodes]

Wall of Force calls out it's interaction because it is an exception to the norm. As disintegrate can only destroy a "10-foot cube portion of it". Wall of Force overrides this to "destorys the wall instantly" not a section, the entire wall.

I think disintegrate definitely needs to counter forcecage from a balance standpoint as well. That's the one real weakness to force spells, that disintegrate can tear a hole in them with no need to dispel and have an ability check against it. Edit: And not even having the option to attempt it means that it's still more difficult to get rid of than most other spells that could trap you.

I can see your point of wanting Forcecage to have something to make it special compared to Wall of Force due to spell level differences. The Charisma check to teleport out is a pretty powerful one, but it is still relatively easy to break out so long as they have multiple attempts and/or a decent Cha save.

Just fwiw I not only find this all to be very fair, after sleeping on it I agree with all of it. Not that it particularly matters for the discussion at hand, for the reasons previously mentioned, but regardless, valid points and agreed.

[GiantOctopodes]

The rule does not specify that the magical fog cannot move through walls so the magical fog can move through walls.

Does the spell create a magical effect or a physical effect?

Cloudkill is a magical effect that can be dispelled.

Why are you applying physics to magic?

Spells apply the magical effect as specified. Magic is not governed by physics. Magic is governed by the rules set forth in the spell description.

The spell creates a magical effect that has physical interactions, just like acid splash, summoned creatures, or virtually any other conjuration effect. Summoned Creatures and Acid Splash also don't specify they can't move through walls, so I guess in your opinion that's fair game as well? I mean if we're going along with the idea of things being able to go through walls unless specified otherwise and all. We'll even specifically ignore the RAW interaction which states that Forcecage blocks spell effects from passing through it, why not. Seems fine, if that's the way you want to run it, you're certainly welcome to do so. Frankly I'm not here to argue you're running your game wrong, no matter how much I may disagree with it.

No one has stated Cloudkill cannot be dispelled, in fact that point has been specifically acknowledged on multiple occasions.

And as far as physics and magic, because the game world doesn't make sense otherwise and I've yet to see a compelling reason not to. Burning Hands and Fireball specify they ignite flammable objects. Flame Strike and Flame Blade do not. Does that mean casting Flame Strike on a barrel of gunpowder would not ignite it, because we don't care about physics, heat transfer, the fact it's doing fire damage, etc, the spell must specifically state it can ignite flammable objects? When you use the spell "Create Water" in an open container, the water does not spread out or flow downhill, because it's magical and thus immune to physics? I mean hey if you want to ignore the part where the RAW discusses relative gas density in a spell description and build a world wherein magic and physics do not meaningfully interact, you do you. Go for it. I'm not going to argue with you, both because it seems unlikely to lead to anything productive, and because it just doesn't matter. I've already stated how Cloudkill works in the game I run. If you want to run it differently you're welcome to, but it's not relevant to the discussion at hand.

[Kane0]

Lower level version: Web or Stinking Cloud + Moonbeam or Flaming Sphere

[GiantOctopodes]

The Cloudkill is entirely a magical effect.

1. When you lose concentration on the spell does anything physical at all remain?

2. If you think physics restricts spells can you explain the physics behind the Fly spell or Misty Step spell?

Numbers added by me.

1. No, nor does anything remain behind of a summoned creature when you cease concentrating. That's irrelevant, and does not make the summoned creature immune to physics while it exists.

2. I've never said physics Restricts spells, I've said physics Interact with spells. Fly being a great example - if you encounter a heavy gravitational force, or a whirlwind (magical or natural), or the spell wind wall, it does not matter whether the creature's flying speed is natural and physical and based on their wings, or is a magical effect due to the fly spell. Physics and spells still interact with them the same, they are not suddenly exempt from the forces of a tornado because their flight is magically based. The strong wind generated by Wind Wall which keeps fog, smoke, and other gasses at bay? In my world, it would also thus keep the gasses at bay generated by a Cloudkill, as it does not care about their origin. Clean and simple. It would not care if the small or smaller flying creatures had natural or magical flight. Everything interacts normally and logically and without issue.

You never answered my questions by the way :smallsmile:

[Yakk]

Cloudkill is an area where poisonous vapours hug the ground. If an area is blocked or cut off, this doesn't cause the other parts to "back up" and stay around.



......
.
. X W
.
......

Casting cloud-kill at location X doesn't mean "it runs into the wall and stops". Every round, 10' of ground near the caster becomes clear, and 10 further away (IF the cloud can reach it) becomes cloudy.

If you capture your cloud in a box or a bucket or a dead end, it still evaporates, it just can't get out.

If you seal a barrel while cloud kill is active, it doesn't keep the poison around forever. You can't launch a barrel of cloud kill in a catapult just because "the gas can't get out".

A forcecage is no different than casting cloud kill in a barrel.

I mean, feel free to rule differently. Like almost everything in 5e, it is ambiguous.

[Kane0]

If you seal a barrel while cloud kill is active, it doesn't keep the poison around forever. You can't launch a barrel of cloud kill in a catapult just because "the gas can't get out".

It would be a real nice upgrade to the catapult spell if you could though.

[Mellack]

A couple of other considerations. Even if you don't agree that the cloud is required to move on as the spell says, it is ended by any strong wind effect. So a 2nd level gust of wind ends the spell. Also, the solid force cage is only a 10 foot cube. That means it fails on anything bigger than size large.

[Damon_Tor]

Also Cloudkill moves itself out of position which makes it not work .I blanked and assumed he was talking about Sickening Radiance.

So yea use Sickening Radiance instead of Cloudkill and consider Wall of Force and Wall of Light for a better combo. Remember, you have a Simulacrum, a Familiar, and possibly a Homunculus and a Tiny Servant and a Skeleton or two.

The cloud moves away from you, not away from wherever you were standing when you cast it. All you need to do is run around the cloud in circles and it will stay mostly in the same spot.

[GiantOctopodes]

If you capture your cloud in a box or a bucket or a dead end, it still evaporates, it just can't get out.

If you seal a barrel while cloud kill is active, it doesn't keep the poison around forever. You can't launch a barrel of cloud kill in a catapult just because "the gas can't get out".


For the first part, you realize that 1) gasses don't evaporate, and 2) that's a contradictory statement, right? For the second, of course not. It would disappear when the spell duration ends, when subjected to a strong wind effect, when concentration ceases, or when dispelled, as described in the spell

Of course this is again beside the point, as it doesn't really matter how Cloudkill does or doesn't work, ideally we're identifying other combos or ways to kill off targets, other ways to counter this combo that might require other solutions for, and generally optimizing how a pair of spellcasting assassins with access to 8th level spells would reliably off their targets. I'm happy to debate how cloudkill works in my own campaign with you if you like, but ideally this would not be the focus of conversation.


A couple of other considerations. Even if you don't agree that the cloud is required to move on as the spell says, it is ended by any strong wind effect. So a 2nd level gust of wind ends the spell. Also, the solid force cage is only a 10 foot cube. That means it fails on anything bigger than size large.

All of this is true, which is why Sickening Radiance is better if you have cause to believe the target is immune to poison, has wind effects available, or is for whatever reason immune to gas effects. Meanwhile Cloudkill is better if you need to for some reason obscure their vision or if you have reason to believe they are immune to radiant damage. That final point is one in favor of Wall of Force - For larger creatures, especially if you can trap them in a corner or something, the more flexible configuration of Wall of Force might let you still get the job done. It still would be convoluted and unreliable vs what Forcecage can do to smaller creatures, but it might at least be possible. Also thank you for contributing to the core of the topic at hand, I appreciate it.

[SharkForce]

the one improvement I would look to making is to try to add in some sort of vision obscuring effect into the mix (pyrotechnics conveniently does not require concentration, and is recommended for this purpose).

it just so happens that in addition to a lot of spells requiring vision, some creature abilities that allow teleportation also require vision :)

[Valmark]

Should probably also include in the downsides that you need to be particular about the order. Cloudkill -> Forcecage allows you to seal off spells, Forcecage -> Cloudkill requires you to use the open cage version, meaning Cloukill can leave.

That said, how about Maelstrom+whatever? It's not the best combo, but I really like it. 30 feet radius of difficult terrain with a Strenght save, be pulled back and receive 6d6 bludgeoning damage. Throw a more effective lasting AoE on top.

Though I'll admit I just like Maelstrom's fluff.

Control Water: Whirlpool has the same idea, but different applications (it works only where you have a substantial body of water while Maelstrom works on the ground too).

[Lord Vukodlak]

The rule does not specify that the magical fog cannot move through walls so the magical fog can move through walls.

The rules do specify that it spreads around corners, if it was intended it passed through solid objects it would specify things differently. By your logic a fireball explosion would pass through a wall and hit people on the other side. Even if no corners were in range of the spell. Or you could put a wall of fire outside the forcecage and the heat would radiate through the wall because it doesn't specify it can't.

So sure you can rule the cloudkill moves through solid objects but you open a huge can of worms you'll be expected to obey to remain consistent.

But lets take your nitpicking to its real logical conclusion.
"The fog moves 10 feet away from you at the start of each of your turns"
All you have to do is keep circling the cloudkill and you can keep it covering the forcecage.

[Valmark]

The rules do specify that it spreads around corners, if it was intended it passed through solid objects it would specify things differently. By your logic a fireball explosion would pass through a wall and hit people on the other side. Even if no corners were in range of the spell. Or you could put a wall of fire outside the forcecage and the heat would radiate through the wall because it doesn't specify it can't.

So sure you can rule the cloudkill moves through solid objects but you open a huge can of worms you'll be expected to obey to remain consistent.

But lets take your nitpicking to its real logical conclusion.
"The fog moves 10 feet away from you at the start of each of your turns"
All you have to do is keep circling the cloudkill and you can keep it covering the forcecage.

To add to this, Forcecage explicitely stops Cloudkill or anything else from leaving in its Box shape.

In the Cage shape there's no discussion since it has explicitely holes for Cloudkill and similar stuff to pass through.

[Lord Vukodlak]

Nope. Walls provide total cover and there are general rules for spells that govern the interaction of spells and objects.

Explain why this does not apply to cloudkill.

[Valmark]

Nope. Walls provide total cover and there are general rules for spells that govern the interaction of spells and objects.

PHB 204

"A spell’s effect expands in straight lines from the point of origin. If no unblocked straight line extends from the point of origin to a location within the area of effect, that location isn’t included in the spell’s area. To block one of these imaginary lines, an obstruction must provide total cover"

So per the rules, the fog keeps moving toward the wall and into the wall until the fog gets shut off by having no lines of effect to the point of origin. If there are holes in the wall then the fog can "spread around corners" as allowed by its spell description..

The rules for Cloudkill need to specify the conditions that stop the movement. No conditions are specified so the movement cannot be stopped.

In the case of an airtight room or container the fog moves into the wall until it shuts itself off. Continually repositioning the spellcaster can allow you to steer this movement annd move the fog back into desired position to keep the fog from shutting itself off.

First off, the text of Cloudkill explicitely mentions physics so you're wrong in saying they don't apply.

Second, Forcecage (Box) explicitely forces Cloudkill to stay inside.

Third, Forcecage (Cage) being open allows Cloudkill to keep affecting those inside from outside (and the caster can move around to keep it in check).

There is no case where the spell stops affecting those inside a Forcecage due to the movement unless left unchecked.

[Valmark]

Please quote the explicit mention of physics.

"The vapors, being heavier than air, sink to the lowest level of the land, even pouring down openings."

[Jinxed_K]

IÂ’ve used a Monk who is immune to poison damage grapple and drag enemies through the cloudkill. If the cloud moves, you just move along with it. Even if your movement is halved doing this, it will still be 15ft, more than the cloudÂ’s movement.

I always took that interaction with walls rule to apply to instant effects like rays or cone of cold to check if the wall will shorten the range. Cloudkill you create a cloud, then itÂ’s governed by its spell effect.
IÂ’d rule if you cast cloudkill in a 40x40 foot room, it will just stay there till it is dispelled or the effect ends since the volume of the gas does not change. Open a low window or a cellar door and it will start to move that way.

[Valmark]

Yup. The point of origin for the fog area of effect repositions itself to directly move along the ground. Then the spell description moves the point of origin for the area effect 10 feet away from the caster to move the fog area of effect.

There is no statement in the spell description preventing the point of origin for the area of effect from moving into a wall. The wall cuts into the radius of the area of effect until the point of origin is within the wall and cannot trace a line of effect into the area within the container at which point the magical effect shuts off inside the container.

You might want to re-read Chapter 10 in the PHB.

That... Has nothing to do with what I said.

Besides that, as said before, Forcecage (box) stops Cloudkill from moving into the wall while Forcecage (cage) has holes to move through, keeping the line of effect intact (of course you gotta stop Cloudkill from moving too far, which can easily be accomplished).

[GiantOctopodes]

There's always the good old "play dead" approach. If the target "takes damage" and "goes down", and a round later he's still not moving (let's say he made a successful Constitution (Deception) roll or something), how many sorcerers would be paranoid to keep baking the target for the full Cloudkill duration? Some of them, but surely not all of them. (And since they're apparently NPC spellcasters, let me put in a plug for giving NPCs psychological and emotional weaknesses such as impatience and arrogance in order to make the game and the gameworld more fun.)

Max sorry I missed this, that absolutely might apply to Sickening Radiance, especially since them being ousted from invisibility might give a false sense of security. Cloudkill heavily obscures the area, so unfortunately you have no way of seeing if your target went down or not, which promotes "baking till done" as it were, for better and worse. I also fully agree with the idea of giving NPC spellcasters psychological and emotional weaknesses, just fwiw. Someone else mentioned being order specific, which is *very* true. It also made me think and realized there's a significant problem - if Cloudkill is cast first, the area is heavily obscured, so you can't see to target the forcecage. You could possibly work around that in convoluted ways but that *definitely* shifts Sickening Radius to the prime, favored spot if it wasn't already.

Now we need a new non-radiant damage AOE to stick in there with them, unless we want to walk a convoluted path. I don't like the Faithful Hound as it relies on hitting with attack rolls, will review the other suggestions tomorrow. I'll also keep trying to find something for spellcasters, right now my idea for how to combo a silence effect (which is really a fine place to start) with a hazardous terrain effect would be to somehow zero out the oxygen in the forcecage, maybe by connecting it with an open portal to a plane without air in it, though I'm not sure how one would achieve that at this point. Or maybe something about holding up absurd weight on indestructible walls of force and then using an AMF to drop the supports on them while also preventing them from teleporting out? Regardless, I'm pretty sure at least one of Silence, Wall of Force, and / or Antimagic Field would come into play. You can also force shunt someone (no save) by having a wall of force intersect their square, though I don't have any meaningful ways to use that yet. Anyway regardless thanks again everyone for your thoughts and contributions, I really do definitely appreciate the replies.

[Valmark]

What you said was a house rule on your part.

What I said corresponds to the rules in the PHB in Chapter 10 that govern spells. Cloudkill is a spell.

Given that I only quoted the text and thus it cannot be an house rule, I'll just assume you're trolling by now and go back to the actual topic.

[Valmark]

Max sorry I missed this, that absolutely might apply to Sickening Radiance, especially since them being ousted from invisibility might give a false sense of security. Cloudkill heavily obscures the area, so unfortunately you have no way of seeing if your target went down or not, which promotes "baking till done" as it were, for better and worse. I also fully agree with the idea of giving NPC spellcasters psychological and emotional weaknesses, just fwiw. Someone else mentioned being order specific, which is *very* true. It also made me think and realized there's a significant problem - if Cloudkill is cast first, the area is heavily obscured, so you can't see to target the forcecage. You could possibly work around that in convoluted ways but that *definitely* shifts Sickening Radius to the prime, favored spot if it wasn't already.

Now we need a new non-radiant damage AOE to stick in there with them, unless we want to walk a convoluted path. I don't like the Faithful Hound as it relies on hitting with attack rolls, will review the other suggestions tomorrow. I'll also keep trying to find something for spellcasters, right now my idea for how to combo a silence effect (which is really a fine place to start) with a hazardous terrain effect would be to somehow zero out the oxygen in the forcecage, maybe by connecting it with an open portal to a plane without air in it, though I'm not sure how one would achieve that at this point. Or maybe something about holding up absurd weight on indestructible walls of force and then using an AMF to drop the supports on them while also preventing them from teleporting out? Regardless, I'm pretty sure at least one of Silence, Wall of Force, and / or Antimagic Field would come into play. You can also force shunt someone (no save) by having a wall of force intersect their square, though I don't have any meaningful ways to use that yet. Anyway regardless thanks again everyone for your thoughts and contributions, I really do definitely appreciate the replies.

As far as non-radiant damage goes...

Flaming Sphere (it's not large but it can be moved), Hunger of Hadar (needs darkvision), Evard's black tentacles, Storm Sphere, Wall Of Fire, Insect Plague, and Maelstrom are all spells one could use to fill a Forcecage.

If one had Devil's Sight they could also use Maddening Darkness.

Also, if casting first Forcecage (box) one could use both Cloudkill and Incendiary Cloud if I see correctly.

You misread my post (which was confusing on my part). I edited my post for clarity. The line you quoted was an instruction in the spell description to resolve vertical positioning of the point of origin defining the sphere area of affect and not an explicit instruction to apply Navier Stokes equations to resolve the movement of the fog.

Let's focus on a related question. According to you does a Cloudkill ever expand beyond the radius defined by the area of effect? Yes or no?

Oh, I see.
So, while it's not explicit instruction you can't say that it just ignores physics.

As for the question no, it doesn't. That's irrilevant to Forcecage though. You have two versions of Forcecage- one that doesn't allow Cloudkill to move through (but which can't be used as GO pointed out with Cloudkill) and another that allows Cloudkill to move through holes, never having to deal with it sinking into the wall.

[Valmark]

If the gas is prevented from expanding beyond the radius then no physics at all is being applied.

Per the spell description, there is an instruction to re-position the point of origin to hug and move along the ground.

There is an instruction to move the point of origin ten foot away from the caster.

There is no instruction preventing the point of origin from moving into a wall.

Spells do what they say they do in the spell description. If you add something to the spell description then you are house ruling.

So? That has nothing to do with Forcecage like I said.

[Valmark]

Forcecage does not prevent the required ten foot move of the point of origin for the sphere area of effect.

If you think it does then quote the instruction in the Forcecage spell description that accomplishes this.

"A prison in the shape of a box can be up to 10 feet on a side, creating a solid barrier that prevents any matter from passing through it and blocking any Spells cast into or out of the area."

Any. You might argue that Cloudkill isn't matter or that "any spell" only refers to the moment on casting, but that's not the only 'legit' ruling.

For completeness:

"A prison in the shape of a cage can be up to 20 feet on a side and is made from 1/2-inch diameter bars spaced 1/2 inch apart."

In this case you have holes through which Cloudkill can pass, so no argument there.

[Valmark]

No 'matter' moves outside the cage. The point of origin moves which Booleans the area of effect as it overlaps the wall of the forcecage. Eventually the point of origin crosses the wall and the magical effect shuts off inside the cage per the rules for Spells in Chapter 10.

When the fog moves it is not being cast. The concentration for the spell is simply being maintained while the point of origin is being moved. No spells are being cast into or out of the area.

The point of origin cannot pass through the box's wall. Sure, like I said you can say that the point of origin isn't 'matter', but that doesn't mean everybody has to think the same. It's ambiguous.

[Valmark]

No rule says that the point of origin cannot pass through the box's wall. It's a reference point for resolving the area of effect. See Chapter 10.

The spell description requires that you move the point of origin 10 feet away from the caster.

Yes, again, your assertion doesn't have any more validity then mine unless you can prove that the point of origin ignores the box's restriction on what can pass through.

[Zalabim]

No rule says that the point of origin cannot pass through the box's wall. It's a reference point for resolving the area of effect. See Chapter 10.

The spell description requires that you move the point of origin 10 feet away from the caster.

Remember, you aren't moving a creature around the dungeon. You are moving an area of effect.

Going off the cuff here, because I'm away from my books, but cloudkill doesn't say to move the point of origin. If it did say to move the point of origin, I don't see why it wouldn't fall under the rules for the point of origin of an area of effect being stopped by an obstruction and taking effect from the point where it intersects the obstruction, as the example of Fireball in the book. Cloudkill says how it creates the fog, then says how the fog moves. I imagine cloudkill moves much like a large swarm moves, obeying the normal rules for movement, almost like it had 10' speed.

[GiantOctopodes]

The point of origin cannot pass through the box's wall. Sure, like I said you can say that the point of origin isn't 'matter', but that doesn't mean everybody has to think the same. It's ambiguous.

There is no point of origin after the spell is cast. It's a conjuration spell, and you are not conjuring a point which radiates out gas in a 20' radius, you are creating a 20' radius sphere of gas. There's a difference. The argument being presented is exactly the same as if someone were to either summon a flaming sphere and then have it trapped in a forcecage and say that the sphere just rolls on through since nothing in the spell says it can't pass through walls, or that attempting to move the spell through the forcecage results in the point of origin passing through the boundary and disappearing. The fog moves each round (by default), the point of origin does not move and then recheck the casting of the spell, that's just not how spells work. Despite assertions to the contrary by certain posters, you are not moving a point of origin and recasting the spell, you are moving a 20' sphere of fog, per the RAW of the spell. If you create a wall of flame and then your sight gets blocked to half of it, it doesn't blink out of existence because it's not a valid target area for it being cast. A wall of stone must be created in a position where it is supported, but if that support is removed (say via Disintegrate or something) it doesn't blink out of existence, it falls. A wall of stone is both a magical effect and, you know, a wall, that can be interacted with, as is a cloud of fog or anything else created by magic.

Certainly people are free to play otherwise if they wish, but at minimum that is how magic works within the context of my campaign. If your campaign operates differently, it may affect what tactics or spells may or may not be useful for the purpose of assassinating people, but at minimum that's how it works in mine. Hope that helps.

Edit: FWIW I know in general you are arguing a position which is not significantly disparate from my own and certain other posters are more arguing the merits of the position I'm arguing against with this post, I just noted what seems to be a common point of disagreement / confusion as it relates to moving effects vs moving points of origin and figured it would be helpful to at least try to add some clarity, hope this didn't come across wrong.

[MaxWilson]

Max sorry I missed this, that absolutely might apply to Sickening Radiance, especially since them being ousted from invisibility might give a false sense of security. Cloudkill heavily obscures the area, so unfortunately you have no way of seeing if your target went down or not, which promotes "baking till done" as it were, for better and worse. I also fully agree with the idea of giving NPC spellcasters psychological and emotional weaknesses, just fwiw. Someone else mentioned being order specific, which is *very* true. It also made me think and realized there's a significant problem - if Cloudkill is cast first, the area is heavily obscured, so you can't see to target the forcecage. You could possibly work around that in convoluted ways but that *definitely* shifts Sickening Radius to the prime, favored spot if it wasn't already.

Good point about heavy obscurement.

Forcecage doesn't require you to see the area in which you're casting it.

Mordenkainen's Faithful Hound is IMO far superior to Sickening Radiance because it doesn't take concentration, so you can pull it off as early as level 9 using Hound + Wall of Force. You don't even strictly need two spellcasters although of course it is faster and gives less opportunity for counterplay from your target.

The attack rolls on the Hound aren't a serious issue since it's invisible (advantage) and typically attacking at around +9, and it's got 100 rounds of attacks before Wall of Force runs out. Even the Tarrasque will die before 100 rounds elapse.

[ff7hero]

Just a note. Cloudkill's mechanics don't say anything about moving "the sphere" as you keep asserting. It moves the fog which is created in a sphere.

[Phhase]

Create Bonfire, then Forcecage in uniform cube mode. Consumes the oxygen, creating destructively low pressure, smoke inhalation hazard, and of course, a vacuum. Rapid repressurization when the cage is dismissed also poses a significant hazard. Only works on things with vulnerable biology, of course.

[BloodSnake'sCha]

We use wall of force with Sickening Radiance or Storm Sphere.

The main problem is that last time we used it VS enemies that healed from electric damage and figured it out too late.

If we have a Spellcaster to cage we add silence to the mix and if needed darkness or fog cloud.

That is the power of a caster party.

Our DM said that if the Wizard wasn't Evil and the Sorcerer wasn't TN he would have made us choose becoming more evil the more we uae it or not use it.

Cloudkill is a nice option but I am afraid to many enemies are immune to it.

[GiantOctopodes]

Create Bonfire, then Forcecage in uniform cube mode. Consumes the oxygen, creating destructively low pressure, smoke inhalation hazard, and of course, a vacuum. Rapid repressurization when the cage is dismissed also poses a significant hazard. Only works on things with vulnerable biology, of course.

I'm hoping to find some way to achieve exactly this - a vacuum will kill off most "standard" spellcasters quite nicely, and without air they won't be able to use spells with verbal components, and that includes virtually all teleport options. However standard magical fire does not rely on external fuel sources and as such does not consume oxygen, or at least I'm not aware of anything which indicates they do. Nor do they produce smoke. Are there any moderately easy ways to carpet bomb an area in non-magical fire you're aware of, like a tar catapault shot we can ignite and launch at them, then trap them in the forcecage? Better still if we don't have to launch it from a catapault and can just teleport it to an adjacent space or something. If we could somehow anchor a silence effect on an object so when we teleport it over there the area is then already silenced, even better.

[MaxWilson]

Every time I come to this thread to see what improvements anyone has on the original combo, I find that you guys are still arguing about Cloudkill's point of origin, and I leave. Just FYI.

[GiantOctopodes]

Every time I come to this thread to see what improvements anyone has on the original combo, I find that you guys are still arguing about Cloudkill's point of origin, and I leave. Just FYI.

Yeah sorry for the mess. I cleaned up my part of it, we'll see if the thread can get back on track. If not, I'll just let it die and recreate it when an appropriate amount of time has passed, incorporating everyone's feedback and input so far. In the meantime I'll continue looking at options for spellcasters, so if that is the thread's fate, hopefully it'll come back better and stronger, and more clearly defined in intent and hopefully thus less prone to hijacking.

[kazaryu]

So for most targets, two high level spellcasters working in tandem to drop a Cloudkill and a Forcecage on a target during the surprise round is an automatic death. They get no reactions during the surprise round to do anything about it, they get no save to avoid being trapped in the Forcecage, and then once they're in it doesn't matter if they can save vs the Cloudkill every round - over the course of its 10 minute duration, or 100 rounds, it deals 500d8 damage, average 2250. It also works on more than one target, if they're close enough together.

Now, it's not an automatic kill vs spellcasters and supernatural creatures who can teleport, if they can make their charisma save to do so. Nor is it against targets which are immune to poison, or which have (between health and available healing) more than 560 HP, as well as both resist poison and a high enough con to automatically pass the save vs the Cloudkill. It would also utterly fail against someone or something capable of creating an antimagic field. Finally, though the Forcecage cannot be dispelled, the Cloudkill can.

That being said, if you have cause to believe that your target or targets do not have those capabilities, it's certainly a great start. If the duo cast from invisibility there's a relatively good chance of this working in most circumstances vs non spellcasters, and a decent chance of it working vs weaker spellcasters. My question / challenge to all of you, is the following:
1) What other capabilities would allow someone to escape from this trap, or survive it? Keep in mind the Cloudkill does damage even to creatures who can hold their breath and / or don't need to breathe, and though it normally moves every round, the Forcecage is a solid cube that prevents any matter or spells from passing through it, so the Cloudkill fog would be held in place. Furthermore not only can the Forcecage not be damaged by any means, it also cannot be dispelled via Dispel Magic.
2) What improvements could be made to this to cast a wider net and / or catch some of those "tough cases"? Assume you have 2 spellcasters of whatever class, capable of casting 8th level spells. I'm also open to non-magical possibilities. This already requires a great deal to work - them getting within 100 feet and getting a surprise round. Making it easier to execute or more guaranteed in that setup is ideal, adding additional complications or requiring them to get the target to a previously prepared location is not ideal.
3) With the same stipulations, what other combos or options exist to deal with some of those tough cases previously mentioned? Keep in mind that the goal is the guaranteed execution of the target, assuming concentration is not interrupted. Relying on a target failing a save, no matter how unlikely it is that they succeed, is not optimal at all.

I look forward to seeing what you come up with!

1. anything that has natural regen is also going to be inordinately resistant to this trap. a regen of 23+ completely negates it (although that is fairly rare). for example someone with regen20 would only need 175-350 hp depending on tehir con save. of course, regen isn't really the most common feature so tis not a huge worry.

2. a) i mean, obviously using sorcerers means you can use distant spell to hit from further away.
b) wall of force instead of forcecage gives you a larger area iirc.
c) obviously as people have mentioned, sickening radiance.
d) having 2 levels of fighter on the assassins means that you can cast both spells on the same turn. which allows you to cast a 3 spell combo essentially instantaneously instead of 2. 3rd spell could be some kind of heavy debuff like blindness (diviner to force a failure) or...uhhhh. gonna be honest idk....something that prevents spellcasting would be pog. (or combo radiant sickness with cloudkill)

3. control weather could go a long way to forcing a target into a predictable location, while also shutting down mass response. so...not really a straight up death combo, but certainly useful for level 13 casters. if you catch the target on the road its basically a guaranteed kill. *and* has the added benefit of it not being obvious that it was magic (well, sometimes).

[Phhase]

I'm hoping to find some way to achieve exactly this - a vacuum will kill off most "standard" spellcasters quite nicely, and without air they won't be able to use spells with verbal components, and that includes virtually all teleport options. However standard magical fire does not rely on external fuel sources and as such does not consume oxygen, or at least I'm not aware of anything which indicates they do. Nor do they produce smoke. Are there any moderately easy ways to carpet bomb an area in non-magical fire you're aware of, like a tar catapault shot we can ignite and launch at them, then trap them in the forcecage? Better still if we don't have to launch it from a catapault and can just teleport it to an adjacent space or something. If we could somehow anchor a silence effect on an object so when we teleport it over there the area is then already silenced, even better.

If this is the case, then make a big, hollow wicker ball coated in pitch and coal tar (loose fibers for aeration). Light, throw at target, use Control Flames to cause it to burn at double speed (It will not do extra damage, but it becomes double bright, and consumes double fuel - including air, presumably). Then Forcecage around that. Quicken it with metamagic if you have to use your action to "throw the fireball".