D&D 5E Polymorph and a Box

[snickersnax]

So what happens when you polymorph someone (say a medium human/humanoid) into a small fish, snail, turtle, small whatever with little or no movement speed, and then pick them up and put them in a small arcane-locked iron box. And then end the polymorph spell?

What happens to the creature and what happens to the box?

What modifications can be made to the box to make whatever your ruling is more deadly if its not already?

Spikes pointing into the box?

Small holes in the box to relieve some pressure?

A larger box that actually has enough volume to barely fit the original creature with small holes that swords can be inserted into?

 

[Oofta]

The short answer is that the box breaks. If the box can't break it's up to your DM. [/I]From the spell ... it is impassable until it is broken ...

How much damage it does depends on the container, but I would rule that a simple wooden box would do 1d6 damage, while a heavy iron box might do 4d6. However, that's a completely arbitrary number I pulled out of my hat so it's going to be up to your dim.

In addition, what happens if the creature is left in an unbreakable box is also up to your DM. Personally? I'd do the 4d6 and say the creature stops transforming until they are released or they suffocate (and die). There are few save or die spells in 5E, and I don't think polymorph is high enough level to qualify for one.

So ask your DM. If you are the DM, make what you think is a reasonable ruling and welcome to the world of "not every situation is covered by the rules".

 

[jaelis]

Just me, I think I'd play that the spell is extended until the box opens. Seems like fun

 

[SkidAce]

The incredible forces involved in reshaping a creature's form and changing its mass and density are so powerful they either break the box asunder or shunt the creature to the exterior of the box, with the reshaping process negating any damage to the creature.

 

[snickersnax]

So for the box breaker / nearest available space people. What happens if the box is a Leomund's secret chest on the ethereal plane? Lost forever in deep ethereal space?

 

[Caliban]

The primal energies released by the transformation to your normal shape in a confined space causes the box to explode outward, dealing 10d6 Piercing damage from the shrapnel to everyone within 20' radius, Dex save for half damage. The subject of the Polymorph also takes 10d6 damage, Con Save for half damage.

Unfortunately, the caster of the polymorph spell also takes 10d6 Psychic damage (No Save) from arcane feedback and their alignment shifts one step towards Evil. They also take another 5d6 DM Annoyance Damage every time they think of doing this again.

 

[Caliban]

So for the box breaker / nearest available space people. What happens if the box is a Leomund's secret chest on the ethereal plane? Lost forever in deep ethereal space?

The ensuing explosion and release of arcane energies interacts with the undefined material of the Ethereal Plane and causes a new plane of existence to be formed. This is how new campaign settings are created.

 

[snickersnax]

The primal energies released by the transformation to your normal shape in a confined space causes the box to explode outward, dealing 10d6 Piercing damage from the shrapnel to everyone within 20' radius, Dex save for half damage. The subject of the Polymorph also takes 10d6 damage, Con Save for half damage.

Unfortunately, the caster of the polymorph spell also takes 10d6 Psychic damage (No Save) from arcane feedback and their alignment shifts one step towards Evil. They also take another 5d6 DM Annoyance Damage every time they think of doing this again.

So mind blank and I can make polymorph bombs.... cool

 

[Caliban]

So mind blank and I can make polymorph bombs.... cool

Sure. It just takes an 8th level spell, a 4th level spell, and a specially constructed box and you can create a 10d6 damage bomb that goes off within 1 hour.

 

[Fanaelialae]

Really, it's the DMs call. I can't recall any edition addressing this via RAW.

I would largely base my ruling on what I consider the situation's "cheese factor". Meaning, are the players trying to get one over on the game? Not to be conflated with the players being clever. Admittedly, this is a fine distinction and an extremely subjective one (I know it when I see it).

While the general advice is to keep your rulings consistent (and this is generally good advice) keep in mind that this is magic, not science. It's okay to sometimes have it behave inconsistently. If anything, it drives home the idea that spellcasters deal with mysterious forces beyond the ken of mortals. That's not to say that you should undermine the stated effects of a spell, but once you're out in the grey edges of unspecified spell interactions you're in the clear as far as I'm concerned.

If I feel like the players are trying to abuse the magic (spam polymorph on every significant enemy until they fail the save and cram them in a leomund's chest) I'd probably have the enemy appear in the nearest space (having been shunted out of the ethereal plane) at an inopportune time. Or perhaps it seems to work, right up until those enemies (having met on the ethereal plane) find a being capable of plane shifting them back.

On the other hand, as a clever one time thing, I'd probably let it work effectively as an auto-kill. Of course, in this scenario any treasure the creature was carrying would be lost/destroyed as well. That's only reasonable, after all.