Can a visual Minor Illusion be moving?

[Dalebert]

Some objects move normally--the hands of a clock, the bubbling water of a fountain, a tinker toy or a music box. Now the fact that most movement would likely come with sound and these movements happening silently would likely clue someone in (unless you deal with it like someone else casting the spell for the audible portion). I don't see anything in Minor Illusion that says the object can't move, though presumably while staying within the 5' cube area. It seems odd that they don't explicitly say that it must remain still if that's the intention.

There is this take on it from the RAW thread.

A185 The Image part of Minor Illusion cannot have any sensory effects, such as animation (a visual effect) which would be required to have the image move.

But when it talks about a visual illusion and says "no other sensory effects", that seems to obviously refer to the other non-visual senses, e.g. sound, smell, or touch.

[SharkForce]

the spell creates an image. strictly speaking, an image does not move. if i create an image of a dog (which minor illusion can't do anyways because a dog is not an object and minor illusion can only create images of objects), that implies it is not moving.

there are further clues (for example, silent image notes that you can make the illusion appear to move appropriately if necessary while minor illusion does not), but that's probably the main one.

so you could make a broken clock, a pool of water in a fountain that is not... err... fountaining? whatever the proper verb is, anyways, or a toy that is lying on its side or a music box that is not presently playing music. but you couldn't make them move.

it's already quite good as is anyways.

[tieren]

I agree with the above poster except for the dog thing. You could totally make an object that looks exactly like a dog, perhaps even superior quality taxidermy statue. (If it can't move or make a sound what's the difference)

[Tanarii]

I think there's some leeway for DM interpretation to allow objects that have a small amount of natural motion. Things like a boiling pot, or blood dripping off the edge of a table, for example. Or not, as the case may be. It is a cantrip, after all.

What you definitely can't make are creatures (objects only), and things that move around. That takes a Silent Image spell or better.

[Ninja_Prawn]

I think there's some leeway for DM interpretation

As a DM, I have no problem with a Minor Illusion including moving parts, as long as it stays in the same place. The difference between Minor Illusion and Silent Image is that Silent Image can move into different spaces (and its volume is like 27 times bigger). I definitely interpret "sensory effects" as sounds, smells and tastes.

[SharkForce]

I agree with the above poster except for the dog thing. You could totally make an object that looks exactly like a dog, perhaps even superior quality taxidermy statue. (If it can't move or make a sound what's the difference)

as written, yes you could make a stuffed dog. differences would be relatively minor, but present (close inspection would reveal stitches, the eyes probably wouldn't look quite right, the nose would not be wet, etc).

[Dalebert]

the spell creates an image. strictly speaking, an image does not move. if i create an image of a dog (which minor illusion can't do anyways because a dog is not an object and minor illusion can only create images of objects), that implies it is not moving.

That's a good point, though there is significant precedence for following the spell's description and not the spell's name which can often be misleading, e.g. Protection from Evil & Good. I don't feel like the description precludes the object moving within the limits of its area.


there are further clues (for example, silent image notes that you can make the illusion appear to move appropriately if necessary while minor illusion does not), but that's probably the main one.

True, but I interpreted that as meant to clarify the limits of it rather than to add an ability, something that was lacking somewhat in previous editions. That seems intended to prevent people from doing things like having the illusion transform unnaturally and things like that. The inclination is to treat it as creating a visual illusion of whatever you can imagine and they're just trying to prevent abuse, like a human transforming into a dragon or a human turning to stone or catching on fire.


it's already quite good as is anyways.

Sure. I'm fine with a DM ruling either way. I don't think it suddenly gets broken from this however. To me that's not as bad a potential exploitation of the RAW as the example below and yet the example below is absolutely possible strictly by the RAW.


I agree with the above poster except for the dog thing. You could totally make an object that looks exactly like a dog, perhaps even superior quality taxidermy statue. (If it can't move or make a sound what's the difference)

You're right. You can do this. I won't try it because I feel like I would just piss off the DM too much with such things. :) To me making a clock who's hands are moving a little or a tinker toy that's wobbling around in a tight circle within the area are more in keeping with the spell's intent and don't seem to over exploit the RAW.

For that matter, strictly by RAW, you could make a dead wolf that's curled up in a sleeping position. A very recently dead body is an object, right? It died of a heart attack while sleeping. See how it gets silly?

[Chadamantium]

I have a side question to this. Can minor illusion move if fixed to a spot. Such as a character wearing a mask made of minor illusion. Does the illusion move with the character?

[SharkForce]

the description of the spell is the part that says it creates an image. nothing in the name inherently implies a still image, but the spell itself says that you can use it to create a noise, or an *image* of an object. so going from spell description over spell name, you get a still image.

not that i think it would be inherently broken to allow it to create a clock with moving hands or something, but as written it doesn't.

[Ninja_Prawn]

I have a side question to this. Can minor illusion move if fixed to a spot. Such as a character wearing a mask made of minor illusion. Does the illusion move with the character?

I would rule "no", because I believe that Minor Illusions are anchored to the spot they are created in. A Silent Image could do it, but it would cost you your action every turn to keep it moving with you. Disguise Self is the best spell for achieving this effect.

[Dalebert]

the description of the spell is the part that says it creates an image. nothing in the name inherently implies a still image, but the spell itself says that you can use it to create a noise, or an *image* of an object. so going from spell description over spell name, you get a still image.

Good point. I should have figured as much.

[Desamir]

the description of the spell is the part that says it creates an image. nothing in the name inherently implies a still image, but the spell itself says that you can use it to create a noise, or an *image* of an object. so going from spell description over spell name, you get a still image.

not that i think it would be inherently broken to allow it to create a clock with moving hands or something, but as written it doesn't.

By this interpretation, Silent Image also creates a still image. It uses the same wording as Minor Illusion, and adds the following passage:


You can use your action to cause the image to move to any spot within range. As the image changes location, you can alter its appearance so that its movements appear natural for the image. For example, if you create an image of a creature and move it, you can alter the image so that it appears to be walking.

Nowhere in that description does it say the image can be passively animated while stationary, only that you can move it from place to place as an action and cause it to animate while moving.

RAW, both can be animated, or neither can.

[GWJ_DanyBoy]

RAW, both can be animated, or neither can.

You've shown proved that Silent Image can be animated while moving. And then the source document is silent regarding what happens when you don't take an action to move it.
It doesn't necessarily follow that both spells would function identically in this undefined space, as again, the source document is silent on whether the two spells are consistent with each other. Though I imagine it would be natural for most DMs to rule that they are consistent, for sake of simplicity.

[tieren]

I would rule "no", because I believe that Minor Illusions are anchored to the spot they are created in. A Silent Image could do it, but it would cost you your action every turn to keep it moving with you. Disguise Self is the best spell for achieving this effect.

But what if you were on a sailing ship while the ship was moving, and tried to create an illusion of a crate (using minor illusion). Would the crate remain stationary as to the planet (i.e. instantly slide off the ship and hang in the air as the boat moves away beneath it) or would it remain stationary as to other objects in the environment (actual crates on deck).

Would the answer be different if the illusion were cast on the back of a wagon or cart?

Would the answer be different if it were used on a floating island or flying castle? A tensers floating disc?

[Dalebert]

Nowhere in that description {of Silent Image} does it say the image can be passively animated while stationary, only that you can move it from place to place as an action and cause it to animate while moving.

Yeah, that actually really bothers me. It does seem to imply a very crappy illusion that stands perfectly still and when it moves, it's hard not to imagine that it does so in a very robotic and unbelievable fashion. I haven't used Silent Image much in games but I'm curious as to how various DMs are going to interpret it.

Like, imagine I make an illusion of myself sitting and reading a scroll. That's probably fine for a little while. I can make a sort of alibi. Now I say the image gets up and walks across the room. Am I unable to make it change positions when it gets to the other side? Can it remain standing and be looking at something on a shelf now?

Also, it certainly seems to be intended that you can combine Silent Image with Minor Illusion for the sound portion. Minor Illusion is not concentration. In theory, it seems I should be able to make an illusion of myself and have it speak by combining the two illusions, but depending on how strict the DM is about that bizarre description, maybe not.

What WOULD make sense to me, since it is just a 1st level spell, is that the image is completely frozen when you're not using your action to animate it. If I'm using my action from turn to turn, it should move as I want and therefore appear more believable. What is absolutely silly to me is what seems to be implied by that odd description--I can concentrate to move it from one place to another and the image will animate to move naturally. So I can make an image of myself and make it's legs move, but I can't use my action to make the lips move to sync up with a Minor Illusion? That makes no sense.

I've got a character with Misty Visions now. I'm curious to see how it goes. I may switch it out for the Disguise Self at will invocation.

[Ninja_Prawn]

But what if you were on a sailing ship while the ship was moving, and tried to create an illusion of a crate (using minor illusion). Would the crate remain stationary as to the planet (i.e. instantly slide off the ship and hang in the air as the boat moves away beneath it) or would it remain stationary as to other objects in the environment (actual crates on deck).

Would the answer be different if the illusion were cast on the back of a wagon or cart?

Would the answer be different if it were used on a floating island or flying castle? A tensers floating disc?

I know, I know. If you try to apply science to D&D, everything falls apart.

Completely off-the-cuff, I'd say the illusion is fixed in place on the 'grid'. On a ship, the ship is the grid, and you can have an illusionary crate. On a wagon, the earth is the grid, and you can't have an illusionary crate. So... :smalltongue:

[GWJ_DanyBoy]

But what if you were on a sailing ship while the ship was moving, and tried to create an illusion of a crate (using minor illusion). Would the crate remain stationary as to the planet (i.e. instantly slide off the ship and hang in the air as the boat moves away beneath it) or would it remain stationary as to other objects in the environment (actual crates on deck).

Would the answer be different if the illusion were cast on the back of a wagon or cart?

Would the answer be different if it were used on a floating island or flying castle? A tensers floating disc?

If the caster can "anchor" the illusion such that it doesn't have any velocity relative to a moving object such as the planet (which is rotating and moving in orbit around a star), then the caster can "anchor" the illusion to any other arbitrary frame of reference.
But that's just one interpretation. Maybe the illusion is fixed relative to the spellcaster at the moment of casting. So if the wizard is standing on terra firma, or on the ship, or on the floating disc, then the illusion works so long as the frame of reference doesn't change it's relative velocity.

Stuff like this is why we use abstraction in games.

[SharkForce]

By this interpretation, Silent Image also creates a still image. It uses the same wording as Minor Illusion, and adds the following passage:



Nowhere in that description does it say the image can be passively animated while stationary, only that you can move it from place to place as an action and cause it to animate while moving.

RAW, both can be animated, or neither can.

it can move if you spend your action. you choose the same location as it's original location (or if you insist, a millimeter away), spend the whole round moving there, and you can then alter its appearance so that it's movements appear natural while doing so (note that you *can* but are not required to make them appear natural... if you want your image of an orc to float around, you can totally do that).

note that movement, as used in the English language, does not mean only walking, running, flying, etc... waving your arms around is movement. jumping up and down in place is movement. moving your mouth as if talking is movement. silent image allows your image to perform all these movements and more... if you spend your action on it.

for more on this, read up on major image, which has the exact same text for the visual component but also allows other illusionary elements including sound. it specifically notes that you can cause your illusion to carry on a conversation (something silent image can't do because silent image does not allow for sound). while it does so in the part where it is noting you can change sound, that only makes sense in the greater context of things if the image can also move in that manner.

of course, a generous DM can interpret things differently, such as allowing the image to make minor repetitive movements (a working water fountain, a spinning water wheel, etc), but that's up to them.

[Desamir]

it can move if you spend your action. you choose the same location as it's original location (or if you insist, a millimeter away), spend the whole round moving there, and you can then alter its appearance so that it's movements appear natural while doing so (note that you *can* but are not required to make them appear natural... if you want your image of an orc to float around, you can totally do that).

note that movement, as used in the English language, does not mean only walking, running, flying, etc... waving your arms around is movement. jumping up and down in place is movement. moving your mouth as if talking is movement. silent image allows your image to perform all these movements and more... if you spend your action on it.

for more on this, read up on major image, which has the exact same text for the visual component but also allows other illusionary elements including sound. it specifically notes that you can cause your illusion to carry on a conversation (something silent image can't do because silent image does not allow for sound). while it does so in the part where it is noting you can change sound, that only makes sense in the greater context of things if the image can also move in that manner.

of course, a generous DM can interpret things differently, such as allowing the image to make minor repetitive movements (a working water fountain, a spinning water wheel, etc), but that's up to them.
I don't disagree that you can animate it using your action. I just think the intention isn't for the object/creature to seize in place like a statue if you don't spend an action.

For all the limitations listed in both MI and SI, "stillness" isn't one of them, so I believe the RAW supports this interpretation.

[Lonely Tylenol]

Sure it can, if it has enough emotional appeal. :smallamused:

I'm under the impression that a spell is not capable of doing something unless it explicitly says it does. This rings especially true for the image line of spells, where descriptions are often cumulative ("as previous, plus..."). In particular, a future spell down this line has specific provisos which allow movement under certain parameters (and not necessarily so outside those parameters), but the spell in question does not have these same provisos. This does not mean that the latter spell lacks the limitations of the former, but rather, the latter is even more tightly bounded such that it is incapable of the freedoms granted by the former in the first place.

In short: "the spell doesn't say I can't" is not RAW.

[MaxWilson]

But what if you were on a sailing ship while the ship was moving, and tried to create an illusion of a crate (using minor illusion). Would the crate remain stationary as to the planet (i.e. instantly slide off the ship and hang in the air as the boat moves away beneath it) or would it remain stationary as to other objects in the environment (actual crates on deck).

Would the answer be different if the illusion were cast on the back of a wagon or cart?

Would the answer be different if it were used on a floating island or flying castle? A tensers floating disc?

As DM, I'd just rule that it's stationary with respect to the local inertial reference frame. So yeah, it would get left behind by the ship.

If the players find a way to abuse that ruling, so be it.

[Dalebert]

The ship thing raises some questions. That can potentially foul of a lot of spells that are supposed to be fixed. On the one hand, I'm not sure it's fair to gimp casters that much. Now you have this fairly common circumstance that broadly gimps casters compared to all other characters or monsters. On the other hand, you potentially drastically alter the behavior of some spells because now you have effects that are supposed to be fixed that are effectively mobile with regard to your targets.

Just imagine casting a Wall of Force inside the ship's hull or a Cloud of Daggers. If you had Water Walking cast and were there to sabotage the ship, now you have spells that are super extra effective for that beyond how they're ever intended to be used. you're not supposed to be able to use a mobile (effectively) wall of force to cut a ship in half!

This is venturing outside of RAW, but it seems like one of those things that they just maybe didn't think through for all the possible circumstances. Consider that the illusion is being maintained by the wizard's mind to some lesser extent even when he's not using his actions on it. This is definitely true to an extent with concentration effects. If so, then his frame of reference is relevant to the illusion. He can't move it around with his mind, but from his perspective say, inside the hull of a boat, is that the boat is still. Even on the deck, the ocean just looks like this flat endless plane and the motion of the ship is difficult to get perspective on.

I don't know the best way to handle it. Just some things to think about.

[Tanarii]

The best way to handle it is to say it moves with the ship. It's only a problem if you start asking why, then trying to extrapolate whatever reason you come up with to some abusive end.

[SharkForce]

The ship thing raises some questions. That can potentially foul of a lot of spells that are supposed to be fixed. On the one hand, I'm not sure it's fair to gimp casters that much. Now you have this fairly common circumstance that broadly gimps casters compared to all other characters or monsters. On the other hand, you potentially drastically alter the behavior of some spells because now you have effects that are supposed to be fixed that are effectively mobile with regard to your targets.

Just imagine casting a Wall of Force inside the ship's hull or a Cloud of Daggers. If you had Water Walking cast and were there to sabotage the ship, now you have spells that are super extra effective for that beyond how they're ever intended to be used. you're not supposed to be able to use a mobile (effectively) wall of force to cut a ship in half!

This is venturing outside of RAW, but it seems like one of those things that they just maybe didn't think through for all the possible circumstances. Consider that the illusion is being maintained by the wizard's mind to some lesser extent even when he's not using his actions on it. This is definitely true to an extent with concentration effects. If so, then his frame of reference is relevant to the illusion. He can't move it around with his mind, but from his perspective say, inside the hull of a boat, is that the boat is still. Even on the deck, the ocean just looks like this flat endless plane and the motion of the ship is difficult to get perspective on.

I don't know the best way to handle it. Just some things to think about.

out of curiosity, what do you imagine happens to the ship if i cast wall of force in front of it that makes it so much less effective at destroying the ship than casting the spell inside of it?

[Dalebert]

out of curiosity, what do you imagine happens to the ship if i cast wall of force in front of it that makes it so much less effective at destroying the ship than casting the spell inside of it?

I guess if it's moving fast enough, it will probably be destructive either way. It does see easier to rip things apart from the inside. I wouldn't expect the guts of the ship to be as resistant. If the ship is going slow enough, then it might just glance off a wall in front of it with minimal damage.

But let's put aside the simple case of damaging a ship. Imagine a well-placed wall or a Cloud of Daggers. Now a spell that's intended to be stuck in one place is moving around relative to your enemies. You can crush the between two moving walls now or place a Cloud of Daggers such that it tears through people and maybe rips through the walls of the ship. I don't know. The spell doesn't even address the situation of what happens when the walls around it are moving. Does it rip through them? Does the spell just end?

I feel like my head as a DM will hurt less and the game will be less broken if you just say that fixed spell effects are fixed relative to the structure that they're in if it's a suitably large structure like a ship or a flying castle. Oh, that reminds me. There's a flying castle in Hoard of the Dragon Queen. Does the module explain how to handle all the complex side-effects of spells that are fixed relative to the planet's surface? I don't think it does. If so, our DM glossed over that technicality and had the effects move with the castle.

[JoeJ]

I think the easiest way to do it is just have it be stationary with respect to whatever it's on, whether that's the ground or a vehicle, with the DM exercising a little judgment to prevent shenanigans (no casting it on a coin, for example). Either that, or have the caster decide (with the same "no shenanigans" caveat).

[goto124]

note that movement, as used in the English language, does not mean only walking, running, flying, etc... waving your arms around is movement. jumping up and down in place is movement. moving your mouth as if talking is movement. silent image allows your image to perform all these movements and more... if you spend your action on it.

How much movement can the silent image perform? If I have an image of a living human, that image would require a lot of small little movements to look realistic, because living humans have lots of small little movements.

[SharkForce]

How much movement can the silent image perform? If I have an image of a living human, that image would require a lot of small little movements to look realistic, because living humans have lots of small little movements.

as written, as much as you need (including explicitly looking natural) if you spend an action, none if you don't... unless your DM rules otherwise.

[georgie_leech]

I guess if it's moving fast enough, it will probably be destructive either way. It does see easier to rip things apart from the inside. I wouldn't expect the guts of the ship to be as resistant. If the ship is going slow enough, then it might just glance off a wall in front of it with minimal damage.

But let's put aside the simple case of damaging a ship. Imagine a well-placed wall or a Cloud of Daggers. Now a spell that's intended to be stuck in one place is moving around relative to your enemies. You can crush the between two moving walls now or place a Cloud of Daggers such that it tears through people and maybe rips through the walls of the ship. I don't know. The spell doesn't even address the situation of what happens when the walls around it are moving. Does it rip through them? Does the spell just end?

I feel like my head as a DM will hurt less and the game will be less broken if you just say that fixed spell effects are fixed relative to the structure that they're in if it's a suitably large structure like a ship or a flying castle. Oh, that reminds me. There's a flying castle in Hoard of the Dragon Queen. Does the module explain how to handle all the complex side-effects of spells that are fixed relative to the planet's surface? I don't think it does. If so, our DM glossed over that technicality and had the effects move with the castle.

So what happens if a Wizard casts Wall of Force in front of their moving ship and then their ship tries to ram another? It seems to me that the spell is just as problematic in that regard. Besides, if a Wizard gets the chance to cast a spell at a ship uncontested, they hardly need shenanigans to wreck someone's day. Plop a Flaming Sphere on deck, fling a Fireball into the sails and rigging, at the highest levels launch a Meteor Swarm from far outside any possible retaliation range.

[Dalebert]

So what happens if a Wizard casts Wall of Force in front of their moving ship and then their ship tries to ram another?

That's an odd question. Then their own ship rams into the wall of force. Why would they do that? I'm certainly not suggesting that just because you're on a boat, the spells cast outside of the boat over the water would also move with the boat. I'm saying if you're on a large moving structure, it's far less complicated and less problematic to have fixed spells cast within it (or ON the deck of it) to be fixed relative to that structure. I mean if it's actually big enough that people are running around on and within it. I don't mean 99% of land vehicles like carts and covered wagons. And I would also say the entirety of the spell effect would need to fit on or within it for this to be the cast.


It seems to me that the spell is just as problematic in that regard. Besides, if a Wizard gets the chance to cast a spell at a ship uncontested, they hardly need shenanigans to wreck someone's day. Plop a Flaming Sphere on deck, fling a Fireball into the sails and rigging, at the highest levels launch a Meteor Swarm from far outside any possible retaliation range.

Sure. I'm not what point you're trying to make with that. How do you handle it when a wall moves through a spell effect, just out of curiosity? The rules don't describe that situation to my knowledge. Give a few examples like flaming sphere, wall of force, cloud of daggers.

[SharkForce]

the DM generally decides what happens.

the flaming sphere is a mobile physical object, with very little mass to it; most likely a wall moving into it will move the sphere, unless we're talking about a wall made of paper or fabric (in which case they will most likely be burnt through) or other special scenarios.

cloud of daggers is a non-mobile, more-or-less indestructible manifestation of magic, but are not noted as having any particular capacity to shove things around or block things (for example, if you placed the cloud on a tight area that a large creature had to squeeze through, the creature would be able to squeeze but would not be prevented from passing through even though the daggers are there, suggesting the daggers do not exist except when they're cutting things). they'll probably inflict some damage on the wall, and magically pass through without destroying (beyond the small amount of damage the daggers do) or being destroyed (again, exceptions exist; paper or cloth will be cut, for example)

wall of force is a non-mobile, more-or-less indestructible manifestation of magic which exists primarily for the purpose of not having things pass through it. generally speaking, the thing that hit it will either bounce off without damaging the wall of force (but may damage itself), or smash itself on the wall of force, or if large enough, the wall of force might pass through it.

basically, you just take the reverse scenario and apply it. what happens when a wall hits a thing? well, what happens when the thing hits the wall?

[tieren]

I think the easiest way to do it is just have it be stationary with respect to whatever it's on, whether that's the ground or a vehicle, with the DM exercising a little judgment to prevent shenanigans (no casting it on a coin, for example). Either that, or have the caster decide (with the same "no shenanigans" caveat).

What if the sea is not calm and the ship is heaving and listing and everything else on deck is bouncing about? Does the illusionary crate remain stationary with regards to the deck which is itself moving up and down and tilting, or to the casters frame of reference to the horizon (such that the deck is dropping out from under it or thrusting up through it).

[JoeJ]

What if the sea is not calm and the ship is heaving and listing and everything else on deck is bouncing about? Does the illusionary crate remain stationary with regards to the deck which is itself moving up and down and tilting, or to the casters frame of reference to the horizon (such that the deck is dropping out from under it or thrusting up through it).

If the image is of something sitting on the deck, it stays sitting on the deck. If it's a Minor Illusion it can't move around on the heaving deck; it just sits there. Depending on what it is, that might be a clue that it isn't real. (A cannon ball that isn't rolling around would be pretty suspicious. A capstan, however, wouldn't be.)

[georgie_leech]

That's an odd question. Then their own ship rams into the wall of force. Why would they do that? I'm certainly not suggesting that just because you're on a boat, the spells cast outside of the boat over the water would also move with the boat. I'm saying if you're on a large moving structure, it's far less complicated and less problematic to have fixed spells cast within it (or ON the deck of it) to be fixed relative to that structure. I mean if it's actually big enough that people are running around on and within it. I don't mean 99% of land vehicles like carts and covered wagons. And I would also say the entirety of the spell effect would need to fit on or within it for this to be the cast.


Then have it cast on the very front of the ship. The point being, I don't see saying that the spell effect is fixed to the ship instead of free floating solves a problem so much as moves it elsewhere. I do think there's merit to the idea that if something is big enough it could act as something to anchor spells to. I'm not sure I agree in the case of ships, but the flying castle mentioned above would certainly qualify. In that regard it's more quibbling over details than disagreeing with the core concept.

Incidentally, the only time it's come up in the games I've been in, it was ruled that such spell effects aren't rooted to the ship. It makes some spells more useful, like Cloud of Daggers passing over a section of ship creating a bigger zone of damage than usual, and others less, like Minor Illusion not sitting on deck like it should and relatively quickly passing through the back. Of course, then you can also get tricky with it, and create the illusion of a wall of force in their way that they then have to either try to maneuver around or hope that it isn't actually a real wall of force...

[Dalebert]

In that regard it's more quibbling over details than disagreeing with the core concept.

Absolutely. The DM has to adjudicate. That's why I said I would expect the entire spell effect to fit on or in the ship for that to be the case. So the wall, for instance, can't just have a corner sitting on the very tip of the ship to be anchored to it. The entire wall would need to fit on the deck of the ship making it useless for ramming other ships.


Incidentally, the only time it's come up in the games I've been in, it was ruled that such spell effects aren't rooted to the ship. It makes some spells more useful, like Cloud of Daggers passing over a section of ship creating a bigger zone of damage than usual, and others less, like Minor Illusion not sitting on deck like it should and relatively quickly passing through the back. Of course, then you can also get tricky with it, and create the illusion of a wall of force in their way that they then have to either try to maneuver around or hope that it isn't actually a real wall of force...

And that's exactly the kind of swinginess I would be trying to avoid. I wouldn't want to make some spells much more useful and others completely useless. I'm much more concerned with being able to use a Cloud of Daggers or Wall of Force to sweep the deck of your enemies than I am with being able to trick someone into thinking there's a crate sitting on the deck.