"So you're Castiel,"
The former angel was silent, sitting patiently on a bed in a motel, watching television. He paid no attention to the stranger in an all-black suit. The stranger had a smile that could belong to a car salesman due to the detached empathy but clear desire to get something out of a person.
"Are you here to kill me?" Castiel said in his monotone raspy tone.
"Why would I wish that," The stranger said with mock surprise. "From your meddling in purgatory, your direct involvement in stopping the apocalypse, the fact you tried to become a god, or maybe because you are still insipidly loyal to the Winchesters, the very humans who've caused you no end of suffering from you helping them."
"Take your pick," Castiel said lazily. "You wouldn't have to do much."
"No, I wouldn't," the stranger said as he sat on the bed watching the television with the angel. "Not with you being mortal."
Castiel twitched, an ocean's worth of anguish, at the reminder of how he was used in a massive sabotage. Angels were depowered, and Castiel spent his days waiting. Waiting either for revenge for half the things he'd done or possibly the chance to do something right.
"It's the latter actually," the stranger said. "I'm here to get you back in the fight."
"Can I trust someone who can read my mind?"
"Who knows," the stranger shrugged. "But since I can read your thoughts, there's no denying how badly you begged, even prayed, for the chance I'm about to give you."
Castiel turned to face the stranger. His face was blank but the eyes carried a spark of determination rekindled. The stranger smiled at the sight.
"There's a danger coming."
"To this world?"
"To all worlds," the stranger said with outstretched arms. "Every realm, every earth, in every dimension. It has fallen to the people like me, the people behind the curtains, to put together a group who can eliminate the threat at the source. You will be the mystical expert; you're relationship of being estranged from and mastering all things supernatural makes you a top candidate."
"What about the Winchesters, or the other angels?"
"Like I said," the stranger stated as he stood. "This a threat to all worlds. And despite your childish fascination with them, the Winchester brothers are not capable of facing this threat. It's 'above their pay grade' as Dean would say. It has to be you."
"I'm mortal, I cannot do more than any other human now."
"That's the best part," the stranger said. "I can use my influence to return to you a moderate amount of your angelic abilities. And of course I have another incentive."
"What?"
"The chance to reopen Heaven," the stranger said. "If you agree, come with me, convince the others in your group to be, save the worlds, and you shall have your redemption."
The stranger offered a hand to seal the agreement. Castiel looked at it, seeing the chance to do something good but remembering all the times he'd been used. But Castiel's greatest blessing and curse was how trusting he was.
He grabbed the hand. As soon he touched the stranger, his power returned, pulsing through his host body with the weight of a moon being squeezed into his body. He staggered, but recovered, confident with the belief that these powers could do great things in his hands.
"I need my coat before we go."
The stranger smiled as Castiel came back with his iconic coat and stern presence. He gestured towards the door which opened to a doorway of light. The two walked together, into the light, into the unknown.