I was wondering if there were any suggestions on how to deal with any situation when they are so closely linked that they technically hold the same space as the kid. Maybe the kid turns into the monster (Hulk or Jekyll and Hyde style), maybe the kid and the monster rotate spatially so the monster takes the kids spot in reality, or maybe the kid's little sister stumbled into that "fake" dark ritual she was performing and is now the avatar of Tharug G'al, but only when he transforms her completely.
Any suggestions for any special benefits or drawbacks we might want to toss into that?
