Jerian:
Defeat the Cosmic Scout, Cosmic Watcher, Cosmic Priest, and Cosmic Lord. You will pick up a fragment of their essence after defeating them. Assemble these parts and you will have a Seal Breaker, a stone that will allow you to travel directly to Ranku and Demon Prince by fooling the Tower's Seal into thinking you a devil.
Bring the parts to me and I can convert them.
"Yes, let me go inside."