Mat smiled at my agreement and proceeded to set off the eternal Winter.
(10 years later)
Mat never did return my ring, but he didn't kill me at least. Mat made himself ruler of the new world not througb wishes but with sheer power, as ruler he let me be his Succubus wife used to intimidate his subjects. Occasionally I would try to organize a rebellion, but Mat would quickly abolish it, thankfully he never knew I was organizing them. His mutant animal plan didn't work and most animal species have died outx so have most humans. One race of animals did survive, no one remembers what they used to be, but now they resemble Zombies, except they are built for cold weather, they also eat people.
Unfortunately, the endless winter began to take a toll on my body and I was slowly withering away, soon I died and since I was a demon I walked the Earth as an unseen spirit, and the world ended just as expected, Humanity died except for Mat who was left alone ruling whatever mutant animals were still alive.