Acid Vials and Catapult

[JNAProductions]

So, I'm running one of my big bad boss boy fights on the playground, and there was a combo pulled off.

Specifically, a couple of minions with the ability to cast Catapult and a couple of bags filled with five vials of acid each.

Acid does 2d6 acid damage on a hit.
Catapult launches the sack at high velocity.

They had four bags, four Catapults, and with a friendly Monk stunning the boss, four auto-failed Dexterity saves. Each one, by RAW, should deal 10d6 acid damage as well as the spell's damage.

That's what I did go with-it's only phase one, so not a huge deal. But it DOES feel kinda wrong-especially since vials of acid are 25 GP each. A lot for a low-level adventurer, but you could easily stockpile a few dozen as a high-level PC.

What would you rule? What do you feel is fair?

[Frogreaver]

So, I'm running one of my big bad boss boy fights on the playground, and there was a combo pulled off.

Specifically, a couple of minions with the ability to cast Catapult and a couple of bags filled with five vials of acid each.

Acid does 2d6 acid damage on a hit.
Catapult launches the sack at high velocity.

They had four bags, four Catapults, and with a friendly Monk stunning the boss, four auto-failed Dexterity saves. Each one, by RAW, should deal 10d6 acid damage as well as the spell's damage.

That's what I did go with-it's only phase one, so not a huge deal. But it DOES feel kinda wrong-especially since vials of acid are 25 GP each. A lot for a low-level adventurer, but you could easily stockpile a few dozen as a high-level PC.

What would you rule? What do you feel is fair?

Sack soaks the acid. A little escapes onto the target. I’d have it do the damage of a single acid vial.

[Eurus]

D&D just does not handle volume issues like this well in any edition that I know of. In 3.5 it was dumping barrels of magically created poison on people, or gallons of holy water. I've had it come up before as a DM (more as a joking speculation than anything a player was really pushing for), and unfortunately I just can't think of any good way to meet in the middle between semi-realistic volume scaling and game balance. In the end, I just waved the DM Fiat wand and said "no, please respect the action economy".

You can't even really rationalize it by saying "well, once you're splashed with acid it's already doing as much damage as it can and more acid doesn't help" because you could absolutely have a party of four PCs all using their actions to chuck acid vials, and that would do four times as much damage as a single acid vial quite reasonably.

[JackPhoenix]

Catapult does what it says, like all spells: Launches a single object. You launch the bag, it flies until it hits solid surface... that being the vials inside... and both take damage, destroying both the bag and the acid on the spot. You're not doing 10d6 damage with level 1 spell.

Alternatively, it works, both the target and the bag take the Catapult's damage, but the vials don't, and drop on the ground in the target's space.

Inb4 "but physics": It's magic, it laughs at physics.

[JonBeowulf]

Shenanigans like this trigger the "if you can do it, then so can the bad guys" clause from Session 0. I don't punish my players for creativity but I try to ensure they understand that my world is as realistic as possible within the game framework. They get props for thinking of it, but I don't want them carrying it around like some kind of "we win" button.

At the same time, I wouldn't unleash something like this on them until they did it for a few encounters. Typically, only intelligent enemies fight intelligently.

[Toadkiller]

Since they only have acid to the extent that the DM provides, I’m not sure I see a huge problem.

[Dr. Murgunstrum]

I’d probably allow it, though I’d be more inclined to allow a bundled net than a backpack.

I’d also allow a martial to simply throw them too.

But a player pulling that stunt is now submitting their inventory and character weights for audit, as I want to know how a character has that many backpacks and how they’re carrying them.

[Sparky McDibben]

Possible complications:


The acid begins to congeal as the magic goes wild! A black pudding, antagonistic to both sides, emerges!
1-in-6 chance a vial breaks in flight
Crafting acid on such a large scale can produce magical runoff, pollution, tainting water sources, sickening animals, etc.
1-in-20 chance each time that they use this combination that it draws the eyes of the gods of magic, who disapprove of someone "abusing" the spell (next roll as disadvantage)
Acid runoff creates difficult or dangerous terrain (5' square of ground turns to acid, causing 2d6 acid damage to anyone who enters the space)

[DarknessEternal]

Catapult does what it says, like all spells: Launches a single object. You launch the bag, it flies until it hits solid surface... that being the vials inside... and both take damage, destroying both the bag and the acid on the spot. You're not doing 10d6 damage with level 1 spell.

Alternatively, it works, both the target and the bag take the Catapult's damage, but the vials don't, and drop on the ground in the target's space.

Inb4 "but physics": It's magic, it laughs at physics.

This covers everything.

[Pex]

It works. You're launching the vials not the acid. The acid falls on the victim when they break. It's a trick Artificers like to use with the Alchemy Jug infusion. It's very good at low levels. Starting mid-levels it's nice, but you usually have better spells to cast and save first level spells for defense, buff, and/or utility depending on class.

It's likely not something the developers thought about, but it's not an I Win D&D exploit. Acid vials are expensive for low level, so you won't have many. It's a significant cost for the Artificer to choose Alchemy Jug as an infusion and prepare it for the day. If you have enough downtime then you can get a lot depending on number of days of downtime.

[Segev]

If all else fails, just do it with one vial rather than a sack. No question then but that one vial shatters and splashes the target. Catapult damage plus 2d6 acid damage; voila!

You're spending a resource on it (the acid isn't free), so it's a little action economy efficient, but not too much so.

[Kane0]

I typically rule you can launch a single acid flask or alchemist fire vial and add the damage of that to catapult, but I do make it clear to players that the max you can squeeze out of catapult by flinging dangerous objects is an extra die of damage.

[T.G. Oskar]

So, I'm running one of my big bad boss boy fights on the playground, and there was a combo pulled off.

Specifically, a couple of minions with the ability to cast Catapult and a couple of bags filled with five vials of acid each.

Acid does 2d6 acid damage on a hit.
Catapult launches the sack at high velocity.

They had four bags, four Catapults, and with a friendly Monk stunning the boss, four auto-failed Dexterity saves. Each one, by RAW, should deal 10d6 acid damage as well as the spell's damage.

That's what I did go with-it's only phase one, so not a huge deal. But it DOES feel kinda wrong-especially since vials of acid are 25 GP each. A lot for a low-level adventurer, but you could easily stockpile a few dozen as a high-level PC.

What would you rule? What do you feel is fair?

The sack of acid vials deals 2d6 damage, but at a larger radius (plus the spell's damage). You're essentially adding volume, not potency.

The best example of how someone like JC would rule it comes from the Meteor Swarm description (curiously, a 9th level spell!):

Blazing orbs of fire plummet to the ground at four different points you can see within range (1 mile). Each creature in a 40-foot radius sphere centered on a point you choose must make a Dexterity saving throw. [...] A creature in the area of more than one fiery burst is affected only once.

Your suggestion would've worked nicely on 3.5, where Meteor Swarm actually increased its damage if you stacked it, but 5e explicitly avoids that. Now, if you were to use all four orbs of Meteor Swarm in a cluster (i.e., within 5-ft. distance), what you'd do is much like throwing a super-powered Fireball cluster and increasing the area of effect by 5 feet (hence, covering only slightly outside the area of a single orb if thrown separately).

Thus, rather than affect all creatures within 5 feet, the acid vials would affect all creatures within 10 feet, and only the targeted creature would be affected by the Catapult spell. Even if the sack absorbs most of the (theoretical) damage, some of the acid will be flung in a ripple from its source with enough strength to double the usual splash radius. However, by DM fiat, most of the acid (which, I presume, the PC wanted to concentrate in a single target) would be consumed on something else which soaks up the damage - the sack.

(Also, note that the acid itself is not "concentrated" in the chemical sense - it's just more acid but also more volume. If you had the concentration of five vials of acid in one, then I'd consider increasing the damage, but as it is, it'd be the equivalent of throwing a beach ball-sized water balloon rather than a typical water balloon - the extra damage would come from the added force of the water's mass, rather than the water's mass itself. Don't take me on that one, but it's the principle I'd use - you may be debated by someone whose physics and chemistry lessons are fresher, though.)

[JNAProductions]

The sack of acid vials deals 2d6 damage, but at a larger radius (plus the spell's damage). You're essentially adding volume, not potency.

The best example of how someone like JC would rule it comes from the Meteor Swarm description (curiously, a 9th level spell!):


Your suggestion would've worked nicely on 3.5, where Meteor Swarm actually increased its damage if you stacked it, but 5e explicitly avoids that. Now, if you were to use all four orbs of Meteor Swarm in a cluster (i.e., within 5-ft. distance), what you'd do is much like throwing a super-powered Fireball cluster and increasing the area of effect by 5 feet (hence, covering only slightly outside the area of a single orb if thrown separately).

Thus, rather than affect all creatures within 5 feet, the acid vials would affect all creatures within 10 feet, and only the targeted creature would be affected by the Catapult spell. Even if the sack absorbs most of the (theoretical) damage, some of the acid will be flung in a ripple from its source with enough strength to double the usual splash radius. However, by DM fiat, most of the acid (which, I presume, the PC wanted to concentrate in a single target) would be consumed on something else which soaks up the damage - the sack.

(Also, note that the acid itself is not "concentrated" in the chemical sense - it's just more acid but also more volume. If you had the concentration of five vials of acid in one, then I'd consider increasing the damage, but as it is, it'd be the equivalent of throwing a beach ball-sized water balloon rather than a typical water balloon - the extra damage would come from the added force of the water's mass, rather than the water's mass itself. Don't take me on that one, but it's the principle I'd use - you may be debated by someone whose physics and chemistry lessons are fresher, though.)

This is what I think I'll go with in the future.

Thanks all. :)