"I'm here to get Magnus his magic and his immortality back," Alex says.
Asmodeus doesn't smirk or make him beg like Lorenzo. He sort smiles, just a little, almost like he's expected Alec to end up here. Alec refuses to flinch because he's here for Magnus. When Magnus broke down on the balcony, Alec still thought he could fix it. He'd listened while Magnus described all the terrible things going through his head. He'd listened, he'd held Magnus close, and he'd plotted. But he's slowly starting to realize that he can't fix it.
Alec stares into Asmodeus's eyes, daring him to say no. He watches as Asmodeus's face turns cold and cruel.
"Under one condition; You end your relationship with him. Break his heart to save his life."
Alex hesitates.
He knew Asmodeuss was cruel. Alec was prepared to give Asmodeus his ruins, his title, his life . Alec figured that it would be a worthy trade. Magnus traded his magic for Alec's life once before, now Alec was just doing what should have happened when Jace pushed that sword against his neck. He was prepared to hurt. But Alec's heart breaks because that was not what he expected. He doesn't want to live in world where . He still remembers the day Magnus broke up with him in the elevator. Alec knows what it's like to see Magnus every day, unable to reach out and touch him. He doesn't think he can go back to that.
Alec almost says no. He opens his mouth to tell Asmodeus to fuck off, but then he hears Magnus's voice.
Don't pretend this is just a phase
Then he think about that box even though he knows he's not supposed to. He thinks about how Magnus had been preparing to put him in that box. Alec's not stupid enough to think that Magnus is actively waiting for Alec to die or imagining his future once Alec is gone. But he's also not dumb enough to think that Magnus had gone into their relationship thinking Alec would be by his side forever.
Magnus is Alec's first love and his last. Shadowhunters love once, and Alec knows that there will never be anyone but Magnus. And it's taken a while but Alec knows now that he'll never be Magnus's last love or even his greatest. Maybe it will take ten years or maybe a century, but Magnus will put Alec in that box, and he will love again. He'll love people far more exciting and wonderful than Alec. He'll love people who won't drag him into Clave politics or cause him to lose his position as High Warlock. Someone else will curl up in bed with him in the mornings. Magnus will tell someone all the things he's told Alec. And those people will make Magnus feel loved and wanted, like Alec once did.
That's the life Magnus wants.
I don't know if this feeling will pass
Alec knows now that he is not enough. When Alec thinks of Magnus he thinks of getting married. He thinks about having a family, and maybe if he's lucky, watching the world from the balcony of Magnus's loft as his hair greys and thins. It's the life that the tiny tiny selfish part of Alec saw when Magnus lost his magic. He never wanted Magnus to go through the pain of having his magic stolen from him. But maybe...just maybe he wanted Magnus to be okay with it.
But Magnus...Magnus wants to continue snapping his fingers to put on his makeup. Magnus wants to have the power to summon portals and fire. When Alec dies, Magnus wants to live.
...for as long as I live.
It sounds more morbid in his head than Alec means it to. But he knows one thing for sure. Alec's unconditional love, his entire heart and soul, means nothing in the face of Magnus's magic. Alec doesn't want Magnus to grow old next to him when it's clear that Magnus dreads their future together. Even if Alec had proposed, he's starting to realize that a dark cloud of resentment and anger would follow Magnus wherever he goes.
Alec's trying not to take it personally. He tries to imagine what he would think if someone stripped him of his ruins and kicked him out of the institute. He knows that he would be devastated. He's spent his whole life training to be the Head of the Institute, and he doesn't know who he would be without it. But, he thinks bitterly, it wouldn't mean anything without Magnus. Then Alec remembers his plan to propose. What a stupid plan.
All he's seen for the last few days has been Magnus's broken expression as he sobbed on Alec's shoulder. And Alec knows that is all his fault. He's been burning to ask Magnus one simple question, but he's been to gutless to open his mouth. Some part of him thinks it's because Magnus isn't in the right state of mind to answer, but mostly it's because Alec doesn't want to hear the answer. He doesn't want to hear Magnus say he would rather have let Alec die than surrender his magic.
So what does it matter if they break up in ten days or if Alec leaves Magnus a widower? Magnus wants to move on. He wants his life to continue when Alec is gone. Magnus has never wanted anything else. He's never wanted to live a moral life beside Alec. And Alec...Alec spent his whole life knowing he would never have what he wanted. How truly fitting that the one time he truly believed he had what he wanted, when he finally found his soulmate, that his soulmate doesn't want him back.
Alec shakes his head. He knows it's not like that. Magnus loves him. Magnus wants him. Just not more than his magic.
Alec looks at Asmodeus again. Asmodeus is studying him, as if he's trying to guess what Alec is thinking. But he looks confident. He knows that Alec needs his help.
Alec looks up for a moment as the tears pool in the corner of his eyes. He has to be strong. He thinks about the way Magnus smiled when they met. He thinks about his cat eyes, and the joy on Magnus's face as he summoned a portal for their date. He wants Magnus to be that happy again. And if all he has to do is crush his own heart, then that's a a price he's willing to pay.
Alec hesitates. But only for a moment.
"It's a deal."