The guy who commanded ghosts who went away a long time ago after getting beat by East? That guy?
Yep.
Spoiler:
He showed up and curbstomped D'arlo/Diabolo (admittedly because physical attacks don't work on ghosts) while acting as the Gatekeeper for North.
Tania immediately and decisively decided to take him out, but she can't see ghosts and only sense them through her spirits, which lowers her response speed. So Monica's Supporter, Paravati, attached itself to her to give her the ability to see them with the condition being it places a huge strain on her eyes and she'd likely go blind in 10 minutes of use. Tania states that's more than enough time since her stones are shaped by the spirits, meaning it gets around the physical limitation that D'arlo couldn't.
So you basically have the two strongest White-Class WH fighting at the moment.