I'm sorry, but I'm abandoning this story. After finishing the first chapter, I got busy, then I got lazy. I never wrote any outline or plans, and ended up forgetting about plot threads I brought up.
The ideas I had for the rest of the general plot includes Gregor being able to see Harry's invisibility cloak because of echolocation, Mrs. Cormaci actually being a squib, some of the living Underland bats that we know (Aurora, Nike, Andromeda) coming to England right before the battle of the Department of Mysteries with Mareth and Hazard, Aurora actually being Ares mate and was pregnant at the time of his death, her child coming to England with her. Everyone would take the fliers to London, Gregor and Mareth would participate in the battle, Sirius would survive, Gregor's adventures in the Underland would be reveled. They would help in the war. That was about as much as I had planned.
The story can be adopted by anyone who is willing to write one.