One day, suddenly... a night where the moon shines like never before, a boy meets the otherworldly Serin, a denizen of Chaos, only to die and become the undead. Now immortal, he can no longer exist with humans due to an ancient law... A tale of revelations that begins as he returns to Chaos, the start of a new adventure!

Sequel to Immortal Regis. Reading the entirety of the prequel is highly recommended, otherwise, this story from chapter 4 on will spoil it and/or be confusing.

Cavalier of the Abyss (so far) is set only in the world of Chaos. There is now a Regis of Chaos.