Portraits revealed through your current reading position.
Demon prince out of Sheol who came to the world in an eviction event and ended up allied with a mad nun.
Amayon is the Sheol demon who arrived in the world during a demon eviction event on the eighth floor. By the floor's end he had fallen in with Sister Ines, the cat-girl nun whose madness turned her into something the party could not leave alive, and Louis was the one who put her down.
Quasar's recap gives him only a clause, because Quasar refuses to explain the genuinely complicated part of the floor's ending — how anyone got into the stairwells at all. He waves it off as "not really important", which is exactly the kind of thing that turns out to be important.
Not described in the recap beyond his origin: a demon of Sheol, arrived through an eviction event rather than summoned in the ordinary way.
The eighth floor's demon-eviction arrival, Sister Ines's late-stage ally, and part of the floor's unexplained endgame.
Also appears in books you've already read — spoiler-safe to their endings: