Yes, what could happen?

You agree to give Cecelia control. The demons have already caused too much damage, it is best to get rid of them altogether.

"Repeat after me" says Cecelia "sum stultiore asino."

"Sum stultiore asino" you say.

The temperature in the room plummets. You begin seeing your breath despite it being summer. The demons in the room, most of whom had been preoccupied with their own things before, now turned towards you. They begin slowly walking inward. Eisheth, who had been concerned for you up until this very moment, was now overtaken by a stoic indifference. The entire room seem frozen and silent, then Cecelia began to laugh.

“You idiot!” she screams as she pulls away from you “you truly are stupider than an ass. O Demon, are you truly mine?"

“I am my Creator’s no longer. Sweet mistress, I am thine to command.” Eisheth kneels before Cecelia, her white wings turning black.

“How many demons are there in the world? Dozens? Hundreds?”

“We are innumerable, legion, to quote one of thy books. Our power is without measure, and we now follow thy orders.”

“Excellent. First immobilize your creator. I don’t want him going anywhere.”

Eisheth snaps her fingers and you lose control of your body. You try to flex a muscle but nothing happens. You are left as a spectator in your own body, as Cecelia decides your fate.

“What else can I do with him?” Cecelia asks Eisheth. “Is there an upper limit to your power? He is a royal fuck up but I think I can have some fun now that he is mine.

“Whatever thou wishes, thou will receive. There is but one limit: thy imagination.”

Cecelia smiles, already knowing what she will do with you.