I'm working on a story that has several worlds but I focus only two of them now. World A is our present, world B is a fantasy-ish one which is very similar to ours but evolution has been different so there are more intelligent species not just humans and some other plantation as well. Magic in some forms are present.
On that world the Moon is partially destroyed and got closer to the Earth because of the changed magnetic fields and/or changed gravity. It happens in a 100 or 1000 years cycle. World B should slowly be destroyed by this.
I'm thinking a past-war leftover (like a big ship or something) floating around the solar system which mass is bigger so it change the gravity as it comes closer to the planet. Also it knock a small piece from the Moon every time.
How and would it be even possible? Does the fact the the Moon is changing has another affect on the planet?