"Lucifer," Michael shakes his brother softly. "Brother, what have you done to yourself?"
Lucifer looks up and smiles weakly, "What had to be done. Michael, you almost sound like you care. Have you...have you forgiven me after all this time?"
"We are supposed to be the agents of Fate. Even in going against Father's wishes, I realize now you were acting out his divine plan, but this...what you've done, it goes against everything..." Michael pulls Lucifer's withered form closer to him.
"The Winchesters are more than our vessels Michael, they are our counterparts. Sam showed me why we were wrong, this whole time. As angels, we're stagnant. We can't evolve beyond what we are. That's why humans are so damn special!" Lucifer spits out the last word and Michael can see a spark of the passion his brother had been consumed by for eons. "But I found a way, Michael. I found a way to claim that one advantage they have for myse-"
Lucifer spasms in Michael's arms and his light fades even further.
Michael thinks he's crying. He hasn't ever done that before. "Brother, please- tell me how to help you. Please don't...don't leave me alone in here!"
"It's Sam, Michael. He needs what's left of me. He's calling me home," Lucifer looks up at Michael, unseeing and calm.
"This is madness! What makes you think you'll even exist anymore! Stay here! Fight back, don't just...you can't just give up. Not you." Michael is shaking in anger and helplessness.
Lucifer smiles serenely, "I'm not giving up. I'm not capable of that. I'm just moving on, I'm...ascending. Don't despair Michael, I've been reborn, and I will come back for you."
The Light is gone, and Michael weeps.