Formless

Without discernible anatomy. A formless creature lacks a solid body, behaving as if composed of gas or liquid. Formless creatures are only susceptible to burning damage — they cannot be harmed by bludgeoning, piercing, slashing, crushing, or draining damage. Formless creatures are also immune to the grabbed, immobilized, and prone conditions. A formless spellcaster cannot perform gestures and cannot recite incantations.