Stiles knows he is not a lot of things.
He's not a hero. He's not stupid. And he's not going to win.
The Nogitsune is old, powerful, and has him trapped, isolated, and drugged. Sure Stiles has some sliver of hope deep in his heart that Scott, or his dad, or hell, even Derek, might be coming even now to his rescue, might be figuring it all out, might save his arse and the day yet again. But there's a counter point melody that sounds like the beep of his mom's heart monitor, and the distant drip water in a basement as Gerald stands over him and he knows that sometimes life beats you down and sometimes people die and you can't win.
Accepting that he is going to lose just means that Stiles can do what he does best. He plans. He pulls that deep well of stubborn from his soul and he thinks and he knows.
He's not going to win, but maybe he can break even.
So as the Nogitsune snarls at him he doesn't say no, he says, let's make a deal.
"A deal?"
"I could let you in. I could. But the next thing you would do is go after everything I love. I know this. You know I know this. You want pain and chaos and fear. You're evil and old and possibly bored, and this is a chance for you to live again. So I want a deal. I'll let you in, and then you'll leave Beacon Hills. We'll go away and you'll never touch my family and friends. You'll have all the death and destruction you want, but it will be elsewhere."
"I can wait little boy. We both know you'll give in. I have no need to make a deal."
"See that's what I don't get. Sure, you think you know how this ends. I'm sure Peter thought he knew how it ended, him all alpha and powerful against a couple of idiot kids, and he ended up crispy and his throat ripped out. I'm sure that Deucalion thought he knew how it ended, with an alpha pack with Scott and us all dead, and where is he now? Nowhere is where. So sure, you think you know how this ends, but you would be wrong, cos if I've learn anything about Beacon Hills is that nothing ever goes to plan. So if you were as smart as you think you are you take the sure thing and you get the fuck out of this town as fast as you can."
"You tell someone who lives off chaos nothing goes to plan here? Not terribly smart of you."
"Yeah, OK, Beacon Hills be all kinds of crazy. But you know what? So is LA, or New York or hell even Afghanistan, and they have 100 times the population or more. 30,000 people in Beacon Hills and even if every single one is crazy, its nothing compared to the millions out there. 5% of any population is so depressed they are soaking in agony. In a town like LA thats like 6 times as many people in the whole town of Beacon Hills. And even more people live in New York. And that's nothing to the same amount of people who have died in the War. So why would you even want to stay here?"
And the Nogitsune cocks its head to one side and considers. Then it smiles with too many teeth, and snarls, "Deal, little boy. You let me in, and I'll leave Beacon Hills. I'll even not come back. You have my word."
And Stiles knows not to trust it, knows it lies and this is a bad idea all around, but if there even a chance to keep his dad safe? To keep Scott alive? Yeah, he is going to take it. So Stiles nods and stops fighting and is consumed in darkness.
The next day the Sheriff is informed that Stiles is missing. There is a note craved into the wall of his room.
I had to. I love you. Stay safe.
No one in Beacon Hills sees Stiles again. In Afghanistan the locals whisper of a fox who walks in the shape of a boy, and in whose wake death follows. Bombings drastically increase in number as the whole region destabilizes, lives reduced to statistics. But such things don't matter to politicians, who have to deal with rising discontent from voters and a possible new war. They placate and discusses, but no one will look for the real reason. It is after all, just a numbers game.