A random schmuck is magically summoned to operate a doomsday plane, aka an airborne command center, after everyone on board died from either radiation poisoning or some sort of magical curse. It's on autopilot but fail-safe needs a human to physically press the retaliation button.
The plane is equipped with a magical AI that is capable of a lot, but is programmatically restrained from pushing the button to start retaliation. It knew enough to use remaining life force to operate the magical summoning system to bring a human user.
The plane promises you can go home if you push the button and end the world.
The AI starts showing you DoD-ass Powerpoint slides to explain how it works but all it needs you to do is press the button.
From the dead bodies on various consoles, you can start hearing radios blaring from their headsets, saying the war is over, one side lost, and the horrors of a brief but limited war. The plane is reassuring you it's all enemy propaganda, push the button.
Push the Button Now.
