I think this would help; you know how Trisha (Ishtar) views the entire game (Golden Playhouse) as fiction and breaks the fourth wall here and there?
Well, Dumuzid (Boss, or Thomas Mutton) does say out of the blue "I swear on the name of Dumuzid, the Shepherd, consort of Ishtar! Your ass is mine, punk! Prepare yourself!" when Vincent is approaching the final boss area in story mode.
Eventually Vincent demands "Show me your face!" to Astaroth, Dumuzid comments "You'll never see his face, not in a thousand years! Besides, isn't knowing his name enough?"
I'm going to go on a lip and say Dumuzid is somewhere on Ishtar's level because of this, and you do end up defeating Dumuzid, but he ends up surviving the Holy Light blast from the door and was shown to be just bruised from it in reality.
And yes, there's Astaroth who says, "I watch you humans from a world high above." Vincent never faces them, but they're someone you talk to in the window every time you reach a confessional, Astaroth serving as one of Ishtar's avatars.
Heck, all the stuff said before about the nightmares? Forget about that, because in the opening to the Axis Mundi Babel stage, Trisha explains the whole purpose of the nightmares was just to find another consort. Vincent ends up scaling and conquering Axis Mundi.