Hydaelyn is a crazy, out of control AI. She lost it aeons ago and now is just stuck in a loop of Must ... Kill ... Darkness. She even sounds like it, she never has a conversation with anyone, she just drones at people in a scripted fashion. Presumably Zodiark is an equally crazy, possibly even more out of control AI. Not sure how Venat and Elidibus fit into my headcanon but I'll squoosh them in somehow!