Air Form. The phiuhl can enter a hostile creature’s space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.

False Appearance. In a volcanic environment, a phiuhl is indistinguishable from surrounding volcanic clouds. If it takes any actions, it becomes visible.

Volcanic Gas. Any creature other than a phiuhl that starts its turn within 15 feet of the phiuhl must succeed on a DC 18 Constitution saving throw or be poisoned until the start of the creature’s next turn. When poisoned in this manner, creatures take 5 (1d10) poison damage, and if the saving throw fails by 5 or more they are also unconscious. On a successful saving throw, the creature is immune to this effect for 1 hour.

Volcanic Heat. Any creature other than a phiuhl that starts its turn within 5 feet of the phiuhl must succeed on a DC 18 Constitution saving throw or take 11 (2d10) fire damage, or half on a success.

Multiattack. The phiuhl can attack twice with Heat Touch and once with Desiccate.

Heat Touch. Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit:  16 (2d10 + 5) fire damage. 

Desiccate. Melee Weapon Attack: +8 to hit, reach 0 ft., 1 target. Hit:  38 (6d10 + 5) necrotic damage.