Complex sentence: He intends to rule North Wales as a Christian king, though he is not such a good Christian himself; upon discovering Morgaine and Accolon's affair, he threatens to expose her if she does not sleep with him as well.
Split into simpler sentences: He intends to rule North Wales as a Christian king, though he is not such a good Christian himself. He uncovers Morgaine's affair and threatens to expose her if she does not sleep with him as well.