Big Yin (named by Larry Linsay) was an intelligent grey bull "superbaboon" who appears throughout The High Meggas. Big Yin lives on the same high meggas world as Linsay, and is the leader of a pack of baboons. He and the other superbaboons used clubs as weapons.
Big Yin watches when Larry Linsay meets Joshua Valienté, and intends to attack Valienté when he is alone.
The name "Big Yin" is a reference to Billy Connolly's nickname.