Reavers have no eyes or ears, they communicate with smells and scents collected by their philia. It is common for one reaver to eat the brain of another reaver after its death to obtain the knowledge of the dead reaver.
Gaborn: Easy friend, remember, we have a reaver fell mage to fight after this too.
2. Terrifying, cannibalistic, self-mutalating savages living in the outskirts of the settled universe in Joss Whedon's Firefly and Serenity.
Book: Of course they are. Too long removed from civilization, of course, but men. And, I believe there is a power greater than men, a power that heals.
Mal: Reavers might take issue with that philosophy. If they had a philosophy. If they weren't too busy gnawing on your insides. Jayne's right, Reavers ain't men. Or they forgot how to be. Now they're just nothing. They got out to the edge of the galaxy, to the edge of the galaxy, to that place of nothing, and that's what they became.
It's 5 am and we'r trying to sleep, go to bed you goddamn reaver!