Complex sentence: Sisay's kidnapping was a calculated plan of Volrath's to lure Gerrard back into battle, so that he could lay his hands on the rest of the Legacy and on the heir himself.
Split into simpler sentences: Sisay's kidnapping was a calculated plan of Volrath's to lure Gerrard back into battle. So that he could lay his hands on the rest of the Legacy and on the heir himself.