A Cerberus is a three headed hound, normally standing between twenty and thirty feet tall. Each head is individual from the other two, having it's own personality, thought process and needs. Think of three people being in the same body, all struggling for control. For the most part, a Cerberus thinks like a pack, thinking and working as well for the well being of the shared body .
A Cerberus is of chaotic alignment, though if one can tame such a beast they will be loyal and do whatever they have to to obey their masters. Most often used as guard dogs.