Here, the mind flayer is described as "a super-intelligent, man-shaped creature with four tentacles by its mouth which it uses to strike its prey." When it hits prey with a tentacle, the tentacle penetrates to the brain and draws it forth, allowing the monster to devour it.

Do mind flayers have to eat brains?

A mind flayer must have a minimum of one fresh brain per month. Any less than that and it suffers physical debilitation, becoming so weak that it could die. Its ideal diet is one brain per week. A mind flayer that consumes one brain a week does not feel deprived.

Can mind flayers eat dead brains?

Everything that is known about Mind Flayers' diet details their consumption of humanoid brains. Mind Flayers are physically capable of eating animal brains, but doing so would give them little to no nourishment.