Enigma, Hidden Sword

"As expected…" When Roy saw the portal suddenly appear and suck Benia in, he knew that his speculation had been confirmed.

The souls of demons from the Abyss all had an Ouroboros Mark, so they were given a unique label, indicating that they were fundamentally different from demons produced in other worlds. This difference actually had the meaning of 'orthodox'. This was why the Abyss was known as the home of demons.

The first demons must have come from the Abyss…