I think that's Athena in the doorway and I've thought since we found out about Erich that she's Igeyorhm.

And I was really hoping since it's called Pandaemonium that we'd see Mateus' Light Emperor/Dark Emperor aspect come into play. Mateus is my favorite villain next to Kefka.

I also saw someone on Twitter compare Mateus' symbol with the way everyone is presented on this and it matched pretty well.