Complex sentence: It is also discovered that Hunter long ago turned traitor to Door's cause, when she gives Door to Croup and Vandemar, in exchange for the magical spear she needs to hunt and slay the great Beast of London.
Split into simpler sentences: It is also discovered that Hunter long ago turned traitor to Door's cause. She gives Door to Croup and Vandemar, in exchange for the magical spear she needs to hunt and slay the great Beast of London.