Venom Pool
COMPLEX HAZARD 18 +30 (legendary) to distinguish between the hazard and the oozes within it; DC 0 Perception to notice the pool
A shallow, foul-smelling puddle of toxic acid blocks a narrow hall (marked with a dotted line on the map), and poison bursts from it when disturbed.
DC 40 Crafting (master) or DC 42 Survival (legendary) to neutralize the acid while within reach of it. Three successes using either skill (or a combination of both) destroys the hazard.
AC 10
Deadly Footing
The area of the venom pool is difficult terrain, and each creature moving through it takes 10 acid for every square of its area that it moves into.
Poison Puff
A creature moves through any square in the hazard's space
The pool produces a 9th-rank Toxic Cloud; (DC 40 Fortitude) at its center. It then rolls initiative.
(2 actions) The hazard uses its first action to spread 10 feet down the hallway in both directions. Once out of the hall, each side spreads in a random direction each round, but they don't go through doors. The hazard uses its second action to move the center of the Toxic Cloud up to 20 feet in any direction to which any part of the pool has line of effect (normally, to encompass the greatest number of characters). If the cloudkill isn't present, it instead uses its second action to produce a new cloudkill, as Poison Puff.
The hazard ends after 1 minute, contracting to its original size and keeping still until disturbed again.
Pathfinder #174: Shadows of the AncientsOGL