The feral idea came from an issue of Wolverine though. Wolverine enters some dumbass fighting tournament, and the undefeated grand master is a psychic who reads people's minds and body language like Cass, and can read every move that someone intends to throw at him the instant they think of it or prepare to execute it.
The guy gets the upper hand for the whole match until Logan realizes the best thing to do is to let the guy keep pummeling him, to the point where he gets so hurt and angry he goes feral.
His brain shuts off and he just begins acting on wild impulses and instinct, and since there's nothing to read, Wolverine mauls the guy (to death I think).