so the basic idea is of an OC with a sacred gear with 13 forms called The 13th Symphony

it takes the forms of the Cloak of Organization XIII with the Nobody symbol on the back with ability to summon up the weapons of the Organization but can only switch weapons every 5 mins and unlock each weapon separately (up to you when they get what) or not

balance breaker would be keyblade armor and being able to switch forms in an instant and/or use them simultaneously

each weapon attribute lets the user have resistance to that element as well as cast spells of the weapon's attribute

whether they fight the same way is up to you as well as if their part of any faction