Karybdus is a follower of Rathma and a keeper of balance. However he's considered mad since he helped Aldric Jitan to summon Astrogha to the world of Sanctuary to "restore" the balance between good and evil. He was banished together with Astrogha into the moon by Zayl
Karybdus had control over the current king of Westmarch - Justinian IV by imposing as his father Cornelius.
Karybdus appears in Diablo: Moon of the Spider.