The companions scramble to get out of the deadly vapors. The heavy, sticky nature of the cloud weighs on their every move, and it takes each of them a few precious instants to find the iron rungs as the acid burns their eyes and chokes their breathing. Then begins a half-blind, mad climb through a fog that feels a thick as mud, but a lot more toxic, until they safely reach high enough to be outside the deadly zone.
A minute or two later, the cloud slowly dissipates, leaving them worse for the wear but free to continue their exploration.
Spoiler
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Perception checks to determine how fast each team member reaches the rungs, then Climb check to determine how fast they climb up.
DC is 15, success means the task is done in 1 round, failure = 2 rounds if missed by less than 5, 3 rounds if missed by 5 or more.
Vershab Perception (1d20+18)[36] Climb (1d20-1)[1]
Turi Perception (1d20+12)[13] Climb (1d20+4)[24]
Lehasti Perception (1d20+5)[23] Climb (1d20+3)[17]
Azkin Perception (1d20+8)[9] Climb (1d20+1)[17]
Characters take acid damage according to how many rounds total it takes them to get out:
2 rounds (4d6)[16]
3rd round, add (2d6)[7]
4th round, add (2d6)[7]
5th round, add (2d6)[10]
6th round, add (2d6)[3]
(I'm going to leave Calathon benched for the time being, unless someone wishes to play him).
Outcome:
Vershab: 4 rounds total, 30 damage
Turi: 3 rounds total, 23 damage
Lehasti: 2 rounds total, 16 damage
Azkin: 3 rounds total, 23 damage
Adding the 9 to everybody for the time the trap sprung, that's serious damage. Enough to kill a low level intruder, but not you guys.