Weirdling
You are a sneaky thief, who lives on a spaceship, which is actually a tree...
You have something special that no-one else has- magic. Your friend crazy scientist discovered a way to make magic out of the weird mushrooms you found on your adventures, which makes your life as a thief way easier. Magic has many forms, for example when on a sneaking mission you can transform into a broom to get access to places by having the house staff clean rooms with you and leaving you-broom behind afterwards.