Mutation Gas (5e Trap)

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Mutation Gas[edit]




This trap is activated by a pressure plate or other activator.


The trap can be disarmed with a DC 15 check with thieves tools. On a failure, the trap springs.


Once activated, a clear mist is released from a vent, filling the room in a 20 foot radius sphere. Every turn a creature takes while still in the gas, they must succeed on a DC 15 Constitution check or their cells begin a mutation from the tables below.

Each mutation takes D4 turns to complete, and progress each turn. As a DM, you decide appropriate effect for their partial state as they are not themselves, but also not quite the mutation. A creature that leaves the mist no longer starts new mutations, but will continue any in progress.

Any restoration or magic dispelling effect cast with slot of 4th level or higher will reverse all mutations on a creature (leaves over the time it took to kick in), and if a creature uses a mundane or magic effect to flush out their systems, any mutations they have will filter away over the course of D12 hours - their Con bonus.

Also, if a creature actively stays in fresh air, eating food, drinking water, and going to the bathroom, their mutations will leave normally over the course of D8 weeks.


Effects do not change clothing or gear. Effects do stack and can invert.

1d12 Mutation
1 Gender Swap
2 Increase by one size category
3 Decrease by one size category
4 Switch race (roll on the table provided by the reincarnate spell)
5 Grows wings, flying speed equal to walking speed
6 Grow spines and claws, unarmed strikes deal D6 slashing/piercing, rips clothing
7 Become a sprite, as though Shape Change was cast upon you
8 Become Amorphous, can't wear armor, but you can fit through small cracks and openings as small as one inch
9 Become aquatic, gain gills and lose lungs, gain swimming speed equal to twice your walking speed
10 Become polymorphed into a random beast of the DM's choosing.
11 Become elemental(as the Shape Change spell), D4, water, fire, air, earth
12 Grow other creatures parts, such as antlers or a tail, or a stinger or web-glands. They don't affect any statistics

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