Smite Me, Oh Dark One
Acerbus hates his job. While he is content to watch and study the mortal races, the other gods constantly look for reasons to destroy their newly-created world. When they finally find an excuse, they command Acerbus to become the Smiter, destroyer of all creation.
Acerbus decides that there is only one way to ensure his own failure and save the world: by becoming an Evil Overlord.