How do you force a celestial to celestial combat? And what do you do with captives?

[Michael Cule]

The angel characters in my game are doing fine at tracking down demons and slaughtering their physical forms.

However, only one one occasion have they managed to attack an enemy celestial on the celestial plane and actually destroy it.

They keep bashing up demons and leaving them unconscious too. There appears little they can then do with them other than send them right back to hell.

Is there any realistic way that you can hold a demon prisoner?

Any way to interrogate them?

Any way to force them into celestial form and liquidate them? (They are always careful to outnumber the demons.)