Source: Bestiary 5, pg(s). 37
Astomoi appear to be made of darkness and have no discernible facial features. Due to their lack of mouths and eyes, they cannot eat and are blind, and sense the world with their minds. Predisposed to asceticism, astomoi have delicate bodies and rarely wear more than rags, if they wear anything at all.
Astomoi don't need to eat or drink, but instead absorb the essence of food and drink through the air, consuming the nutrients of the meal as though it had been eaten, rendering the food inedible. Since they never actually ingest anything, they are immune to ingested poisons, but are vulnerable to powerful smells and inhaled poisons.
Astomoi pursue enlightenment through self-denial and are psychically attuned to their surroundings.