User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-96.41.73.217-20150821174625/@comment-6344309-20150824062611

Toe Knee 17's theory makes the most sense. God might have created the Leviathans to help him battle the Darkness, but the Darkness was able to twist them and use their vast hunger to turn them against God. So God must have realized the danger they would have posed on the rest of his planned creation, so he had to go out of his way to create Purgatory to lock them away. After that, he realized that he needed to go in the complete opposite direction when creating the Archangels. Adding to that theory, I have a feeling that more than just four archangels were created, and the four we've all seen were the only ones to survive.