Formless

Without discernible anatomy. A formless creature lacks a solid body, behaving as if composed of gas or liquid. It cannot be harmed by bludgeoning, piercing, or slashing damage. It can take damage from fire, but cannot gain the burning condition. Formless creatures are immune to the bleeding, grabbed, immobilized, and prone conditions. A formless spellcaster cannot perform gestures and cannot recite incantations.