My guess is the sword would be an item that grants the wielder their power, but also controls the wielder's mind. The warrior spirit is the blade itself, the body simply serving as a vessel to carry the sword and do its bidding.
Such a character would probably be named after the sword. This could lead to some awesome opportunities for character customization, since you could give the body wildly different traits to represent different bodies carrying the sword.
Zombie trope incoming, perhaps?