This is the «Demon Lord of the Mind». For others who are also called Demon Lords go here.
«Demon Lord of the Mind, Enkvaros» is the second Demon Lord of Cross Reverie.
Enkvaros is the second Demon Lord of the game Cross Reverie. Diablo was the first player to solo defeat it.
In the other world, it was defeated by an unknown person.
It had the power to reflect magic directed at it.
«Demon Lord's Ring»
The Demon Lord's Ring grants the wearer the ability to reflect Magic. Offensive magic and supporting magic like healing are all reflected.
Diablo was the first player to defeat him in the game, he was also the only one to acquire the demon king's ring with the power to reflect magic.