So who's Seddok?

Okay, so I've seen this film a couple of times, but, for the life of me, I can't recall anyone in the film named "Seddok." So who is Seddok and why is he/she the heir of Satan? Is Seddok Lavin's alternate name when he's in his monster form? Is Seddok someone else, and I just haven't figured out who? The identity of Seddok…just one more nonsensical thing about this crazy movie!