About ten years after King Arthur died, the Isle of Avalon, and the city of Camelot were separated from our world by magic. It became it's own realm. Held in a magical bubble to protect it from the world. Or, was it to protect the world from it. No one really remembers why, or even how anymore. All they know are the stories that have survived.
Life went on like normal. Until it didn't. Until one day, a stranger walked out of the mists surrounding the island. A stranger who wasn't even from the world outside, they were from a different world, a different timeline. And, it didn't stop with them. More started coming, and they needed to figure out how, and why.