you have extreme expertise and have bonded with your weapon to a point where it can never be wielded by anyone else.

you can manipulate your weapon through the air at will allowing you to not carry it on you but it float beside you,your blade gains 10 ft more attack range.

you can manipulate the shape of your weapon at will allowing you to make it into the shape of two other melee weapons of your choice that you are proficient in(separate feat allows you to change the blade into ranged weapons as well).

your weapon becomes tied to a accessory which can transform into your weapon that is on your person at all times ex. an onyx locket in the shape of a dragon's head