Aziraphale

After Aziraphale left for heaven with the new position of chief archangel, he and Crowley had a big fight. He, of course, tried to offer Crowley that he could restore his angel status (because Crowley is a rotten angel). And so the war between hell and heaven was in full swing, and the Angels won. After another battle, one of the captured demons was brought to Aziraphale so that Aziraphale would kill this demon. The demon himself was wearing a cape and a hood and had black wings. The demon was forced to kneel before Aziraphale, and Archangel Michael said

We want you to kill him.

Aziraphale, puzzled, asked why
And who's hiding under the hood?

Archangel Michael pulled the demon's hood off, revealing... Crowley. Aziraphale froze.

You are Crowley's demon, Aziraphale's angel.