Tales of Tolgard
When one of these aberrations overcomes a lone victim, it consumes the victim’s brain and enters the skull. The devourer can merge its form with that of a helpless or dead creature.
When an intellect devourer completes its merging, it psionically consumes the brain of the victim, which kills it if it is not already dead. The devourer can exit the body at any time bursting the victim’s skull and resuming its normal form.
After consuming its victim’s brain, an intellect devourer can instead choose to animate the body for up to seven days as if it were the victim’s original brain. It assumes the physical qualities and ability scores of the victim, as if it had used polymorph to assume the victim’s form. As long as the intellect devourer occupies the body, it knows the languages spoken by the victim and very basic information about the victim’s identity and personality, but none of the victim’s specific memories or knowledge.
An intellect devourer has blindsight out to 60 feet.