Breathtaking Vapor

This colorless mist has a mild, waxy scent that precedes acute shortness of breath. Creatures that don't need to breathe can still take the poison's damage but are immune to its other effects.

Saving Throw DC 38 Fortitude; Onset 1 round; Maximum Duration 6 rounds; Stage 1 6d6 poison damage, drained 1, and can't breathe; Stage 2 8d6 poison damage, drained 2, and reduce remaining air by 1 additional round; Stage 3 10d6 poison damage, drained 3, and reduce remaining air by 2 additional rounds

Magical