Rules on add on's like Kenpachi's eyepatch and such. Things not directly upon your character that comes with a character like a zanpaktou and a shinigami need eachother to exist.
In Hisotry Add Ons: If you are a character that has gained someting in your history that is an add on your history must be at least 1500 words and you must have your character be an elite with an administrator's approval. No exceptions.
IC add ons. If your character gains an add on IC then you have a scientist character create it for you through the rules of invention creating and you yourself must make a post of mastering it with that an administrator decides would be fair for the challenge of mastering something like that.