If I cast Enlarge on a vial of acid then cast Catapult on it, will it do 8 times the damage?

Question

My wizard wants to do a spell combo, it will take two turns.

Enlarge/Reduce then Catapult:

1. Cast enlarge on a vial of acid. It weighs 1 pound and per the spell description it will grow to 8 pounds. So it will have 8 times the volume and therefore it will do 8 times the damage. 16d6 instead of 2d6.

How to deliver it?

2. Cast catapult on the large vial at level 2, because it weighs 8 pounds now, doing 4d8 damage + 16d6 acid.

A whopping 128HP max. Average 74.5 (if it hits)

The 5E Player's Handbook page 237. says

The target's size doubles in all dimensions, and its weight is multiplied by eight

The acid vial will weigh 8 times as much so I am simply assuming that there is 8 times the amount of acid

Does this work? If not, why?

Answer 1

Enlarge/Reduce does nothing to change the damage of Vial of Acid.

Enlarge says:

The target's size doubles in all dimensions, and its weight is multiplied by eight. This growth increases its size by one category-- from Medium to Large, for example. If there isn't enough room for the target to double its size, the creature or object attains the maximum possible size in the space available. Until the spell ends, the target also has advantage on Strength checks and Strength saving throws. The target's weapons also grow to match its new size. While these weapons are enlarged, the target's attacks with them deal 1d4 extra damage.

If you use Enlarge to enlarge a vial of acid, all it does is make it bigger. That's it. It doesn't change the damage, because nothing in the spell says it changes the damage. See here for more details on "spells only do what they say they do": What is the source of the "spells do only what they say they do" rules interpretation principle?

This seems pretty intuitive from a balance perspective. Vials of Acid are 25 gp, Enlarge/Reduce is a 2nd level spell, and catapult is a 1st level spell. Combining these very early game features shouldn't produce an effect more powerful that many 6th and 7th level spells.

That said, enlarge adds 1d4 to weapon attacks made by the enlarged creature, so it's probably fine to add the 1d4 when throwing the vial as an improvised weapon per its description.

Using catapult can deal 4d8, but doesn't activate the acid.

Catapult, which has a casting time of 1 Action, says:

If the object would strike a creature, that creature must make a Dexterity saving throw. On a failed save, the object strikes the target and stops moving. When the object strikes something, the object and what it strikes each take 3d8 bludgeoning damage. [Up casting to 2nd level adds 1d8 damage.]

However, Vial of Acid says:

As an action, you can splash the contents of this vial onto a creature within 5 feet of you or throw the vial up to 20 feet, shattering it on impact. In either case, make a ranged attack against a creature or object, treating the acid as an improvised weapon. On a hit, the target takes 2d6 acid damage.

These are two entirely different features that both require an action and cannot be used at the same time. You cannot both catapult and get the acid damage. You must choose one.

Answer 2

No, because only the vial is enlarged, not its contents

This doesn’t work because the spell would not enlarge the contents of a vessel - only the vessel itself.

First, the spell enlarge/reduce is explicit about what it targets (emphasis mine):

You cause a creature or an object you can see within range to grow larger or smaller for the duration. Choose either a creature or an object that is neither worn nor carried.

The spell treats these targets differently, specifying:

If the target is a creature, everything it is wearing and carrying changes size with it. Any item dropped by an affected creature returns to normal size at once.

Obviously a vial of acid is an object, but on page 246 of the Dungeon Masters Guide we have a more explicit definition of how to interpret an “object”:

For the purpose of these rules, an object is a discrete, inanimate item like a window, door, sword, book, table, chair, or stone, not a building or a vehicle that is composed of many other objects.

While a container of a substance is not specifically mentioned, the intent of the rules is clear: that spells targeting objects work only on a single discrete item. So targeting a vial of acid would enlarge the vial, but not enlarge the acid inside, which is not part of the discrete inanimate glass vial. Note that the acid doesn’t meet the definition of an object itself; spells that target water or other liquids are very explicit about this. A strict DM might even rule based on this definition that the vial’s stopper would not be affected, since that is also a discrete object and not a part of the vial in the way that a page is part of a book or a hinge part of a door.

This interpretation of the rules also prevents enlarge/reduce from freely producing large quantities of any liquid, powder or other substance that can be held in a container. While it would only last for a minute, that would be long enough to make finding certain spell components or special materials trivial. Think about this being used on holy water, alchemist’s fire or silver dust!

A generous interpretation could take from the creature rules - the vial’s contents are enlarged, but only until the vial is shattered or the content is otherwise spilled, at which point it “returns to normal size at once” just like something dropped by an enlarged creature.

Answer 3

Since nothing in RAW indicates that more acid = more damage, one can assume that a single flask of acid is enough to splash a whole target, more acid would just miss or have no additive effect.

However, since Enlarge can last up to a minute, you could use it to increase the amount of acid in your flask enough to let you make 8 separate splash attacks with it (each an action, so probably taking 8 rounds) before the spell expires. Or your DM might allow you to increase the area of effect, perhaps targetting 2 adjacent in-range targets with one splash attack. (This would make it like a double-damage version of the Acid Splash cantrip.)

In conjunction with casting Catapult, you might ask the DM to treat it as an area-of-effect splash attack with a 10' radius or 15' cone or something like that. This would be somewhat comparable to a Dragonborn's acid breath weapon and would probably call for a DEX save for half damage.

Answer 4

The glass of the vial would be twice as thick.

A vial, especially one constructed to hold acid, is a very sturdy container. If one were easily broken, no one would carry them around on an adventure.

If we assume the glass is a 1/8th of an inch thick, then enlarging it would result in 1/4th of an inch thick glass.

Catapulting it into a stone wall would probably be enough to shatter it, but hitting a living creature most likely would not. It makes for a great bludgeoning instrument, but I highly doubt it would shatter as expected and coat the target in acid.

As a long-time DM myself, I would probably rule that it does only the catapult damage but the acid inside would still be safe and sound - maybe spilling out the top if there were no stopper.