The Cage is silent.
That might be what breaks him.
Michael has felt the low ache of abandonment. It has carved its way into the core of his grace, and in turn, he has built himself upon its shaky foundations. Every facet of him, every action and dedication, all to fill that hole. He can withstand being left. It's what he deserves, failure that he is, dragged into Hell by a human.
(By his own fatal need to reach for Lucifer. How could he let him go? He was right there, as beautiful and terrible as Michael remembered, and he wanted Lucifer to die in his arms, where he could hold his body as his life drained away. Sam Winchester tried to take Lucifer away from him, and Michael couldn't let him.
So, they fell together. Whatever test that was, Michael knows he failed.)
He knows abandonment. He does not know loneliness. Heaven had grown cold and stiff as a corpse, but his siblings still whispered to each other. Funerals are not silent. Graves are. The Cage is a tomb. Michael can't bear it.
Desperation strikes madness in him. He tries to restrain himself. He prays, but only hearing himself in the emptiness is worse than nothing. He knows the prayers reach no one, not his siblings, not his Father. He knows that all he has left to ask for is forgiveness, and he's not going to be granted it. He had one purpose. One. It rings through his grace so many times that he can almost fool himself into hearing the accusations like they come from anywhere but his own mind.
And then. Then. He begins to panic.
He can't explain it. He knows it isn't possible. He was there when the Cage was built, and he knows how it functions. But still. It's getting smaller. He can see it getting smaller. The bars are caving inwards, and when he retreats, he only finds another wall, cold and unrelenting. It heaves in towards him as well, and Michael launches himself in another hopeless direction.
He doesn't stop to think about how, if the Cage was getting smaller, then Lucifer would be close enough to see, to touch.
He doesn't think at all.
For the first time in his existence, Michael learns helplessness. The lesson sears itself into his being. He knows he will die if he stays in here. He'll be crushed. He needs to get out.
Without hesitation, Michael throws himself against his prison. It burns him back with every thrash of his wings against the cruel metal. He barely registers it, beating himself harder and harder against the wall. He claws at it, scratching deep grooves into the bars. Every time he attacks, he has to make new tears, the old ones vanishing the moment he pulls back to swing. If there was any way to leave lasting scars on the Cage, maybe he'd be able to see that he isn't the first to try and fight his way out. Maybe that would drag him to his senses, knowing how useless his struggle is. But the Cage has no marks on any surface, and so he keeps going.
Even when he starts to feel the pain, he can't stop. His wings grow tattered, threatening to break under the force they hit the wall with. His grace begins to rend, the Cage lashing back out and dealing back the damage he's tried to do to it. By the time he wants to stop, he can't. He fights against his own will, throwing himself into the bars again and again and again and again...
Lucifer is only strong enough to make him stop because Michael's beaten himself half to death. His brother seems to come from nowhere, swooping in on Michael's broken form as Michael weakly fights an opponent that cannot even be dented. Michael doesn't even have the energy to be afraid that Lucifer is taking the opportunity to kill him. He's in so much pain, and he can't stop, and at least, if Lucifer ends it, it won't hurt anymore. Instead, Lucifer pulls him back from the wall and further into the Cage.
Michael struggles but not for very long. Whatever wild drive he had to escape abandons him when Lucifer flattens his wings over Michael's owns to keep them still. Michael collapses.
"Michael-"
That's all Lucifer manages to say. His name, and nothing more, and Michael, subsumed in silence for seconds-years-eternities, twists towards him with newfound energy. Lucifer immediately tries to release him and get away. In the brief contact of grace they share, Michael can feel fear spike in him. He's afraid of Michael, even in this state. Michael has no intention of hurting him (if he still has the power to).
He presses into Lucifer, grace open and receptive in contrast to Lucifer's as he tries to freeze Michael out. Michael only insinuates himself closer, searching for minute fractures in Lucifer's defense that have always existed. They're still there, and Michael's grace seeps through until he can feel his brother and knows him to be real, not another trick of the Cage.
"Speak," Michael begs him.
Lucifer falters.
Cautiously, he comes back. His wings (mangled as Michael's own, now that he can see them clearly, though his scars are long since healed over) fall back over Michael's. He tests how much pressure he can apply, and Michael folds under him, anything to keep him here, to have the chance to hear his voice again. Michael can't go back to silence. He would rather Lucifer let him continue in his suicidal attempt to break free than go back. Lucifer draws him in until they're tangled in an embrace.
"There's no way out," Lucifer says. "Don't you think I would have found it if there was?" Michael shudders as his brother's voice washes over him. His grasp of Enochian is archaic and some words are almost incomprehensible, but Michael understands him. Theirs is a language beyond the one shared by all angels, born when they were the first and only two beings to be created, back when Lucifer was as much a part of Michael as he was his own being. Lucifer could whisper complete nonsense to him, and Michael would still understand every word.
Lucifer's feathers brush against his own. The pain is dulling, slowly. Lucifer's presence soothes it, or at least, keeps Michael distracted enough that he doesn't notice how much it hurts anymore.
"You aren't allowed to die," Lucifer says, quieter. "You aren't allowed to leave me here alone again." In response, Michael digs into Lucifer's grace, rougher than he should given how gentle Lucifer is holding him but he needs Lucifer to understand. That promise has to go both ways, if he's to make it. Lucifer winces, but then Michael feels him bite into his grace in return, harder and harder until there's a new, sharp pain that Michael relishes because it came from Lucifer. Closer, they tangle themselves, like Lucifer isn't so broken he doesn't fit anymore, like Michael belongs to Lucifer before their Father.
Soon, Michael can barely tell where he ends and Lucifer begins. The wounds Michael inflicted on himself trying to escape bleed into Lucifer's grace. Lucifer hasn't stopped talking to him, though his words (demanding, possessive, hungry) betray that Michael hasn't been suffering alone in here. And Lucifer purrs with pleasure every time he insists that they will be left to rot down here and Michael only answers with, "Together. Left to rot down here together."
No more silence.
If he cannot have freedom, he will have Lucifer.