An Old God created by accident. A society of pacifists attempted to excise their negative emotions by collectively banishing them to the Nullspace. These latent feelings of hostility and aggression were given form, becoming a formidable entity.
Cultists of Trigon were able to use a surrogate female to harbor his essence, and from that union Raven was born. She is the key to the lock that holds Trigon at bay. His arrival in the universe would prove a threat of almost imaginable scale.