The Castle was built by Lessa and Ares over 1,000 years, while they repented for their sins. Lessa repented not letting Ares die, while Ares repented for killing humans. When Lessa realised that Ares didn't really repent, Lessa released his powers nearly destroying the castle. Ares horrified that the castle might be destroyed and realising he'd upset Lessa went back on his words and Lessa calmed down.
