Visitor
The Ultimatum
Somebody out there has been counting the nations you erased.
Long, triangular ships take station over the planet as if they own the view. Their first transmission is not a greeting. It is a list of Earth's violations.
They come for a winner who got there by wiping other peoples off the map. Destroy enough of your rivals and the odds turn. Never all the way: nobody can force them to come, and nobody can be sure they won't.
Every other visitor happens to you. This one asks a question, and the answer is yours to give. The Dome does not defeat them; it only decides whether refusing is a fight or an execution.
Comply, and the game is over. Refuse, and you will need the Dome.