[[ Non-HOH compliant (I basically ignored all of HOH for this but I've been dying to write this one shot since MoA came out) ]]
It wasn't a quick decision.
They'd been discussing the Doors of Death for awhile, and although everyone knew that someone had to stay behind, but they all pushed it out of their minds.
Everyone except Leo.
It was the most obvious choice. He didn't have anyone he needed to be there for, he didn't have anyone waiting up, and eventually, they'd get over his death. Dying wouldn't be so bad, not really.
So he'd chosen, a long time ago, that when they got there, he'd volunteer. And then he'd changed his mind. If he volunteered, they wouldn't let him go. He'd make a break for it. They'd get Percy and Annabeth out and he'd run in, closing the Doors from the inside and hoping they realized it was too late by then and closed them from the outside.
So when Percy and Annabeth stumbled out of the doors, collapsing almost right away, Leo didn't stop for goodbyes. He didn't stop to say he was sorry, although he was, and he didn't stop to explain himself, although he wanted to. He just ran for the Doors, the yells of the others and the hands trying to stop him feeling almost distant.
I'm going to die, I'm going to die, I'm going to die...
And then he was on the inside of the Doors, shouts of "Leo!" and "Stop!" suddenly loud in his ears. He doesn't want to face them all. But he does, turning around and trying to draw the Doors closer.
He tries for a smile, but even he can tell it's pathetic. The Doors are heavy, and they won't move, but he thinks that's because no one else is helping. Close them, you morons, close the Doors!
He wants to explain that he's planned this all along, that it's for the better, that he was never really needed much anyway, that he's sorry the Argo controls are overcomplicated. That he's sorry he fired on New Rome, that he's sorry for every fuck-up before and after. But one look at their faces say they get it.
"Help me!" He yells, looking over his shoulder, and immediately squeezing his eyes shut and turning back around. Oh Gods, oh Gods...
It's Nico di Angelo who steps up first, hands on the Doors, and finally, they start moving. His gaze is the only steady one, and meets Leo's easily. He doesn't say anything, just starts moving the doors, and looks at Leo with an expression he knew very well.
"Tell them I'm sorry, and that it's for the best." It's not a yell anymore, because he's too tired to yell, to scared to yell. He wonders if Nico's heard it, but the other demigod gives a nod. He doesn't disagree, and for a moment, Leo wonders whether the creepy Hades kid and him are so different after all.
It's still not going fast enough when the others unfreeze, or come up with the will to help, or something. Leo notes that some of them are crying, and he wants to look away, but looking at them is better than looking at what he's going to face.
Nobody says anything until the Doors are almost completely closed, and then Leo yells, "Don't forget about me! Make bad jokes in my memory!"
And then the Doors are shut, and he's leaning against them, knowing they're shut for good.
It only really hits him then.
This is the last place I'll ever see. I won't ever talk to anyone again, I won't ever go outside again, I won't ever be anywhere but here. Maybe forever. How slowly can monsters kill demigods?
He chokes back a sob, before remembering that it doesn't matter anymore. It's as though his legs can't hold his weight and suddenly he's on his knees with his head in his hands. He wants to stop crying but he can't, because every bit of strength he has was used to close those stupid doors, and now he has nothing left.
I'm sorry, I'm so sorry...
He doesn't have time to think anything else.