Enhance Host

A sword infused with a primordial spark targets a willing or soulless creature, rolling an intelligence saving throw, the Blade fully possesses the target. This target is now treated as a "host" for the Blade, and the Blade can no longer act independantly. Once incontrol, the host gains the combat reactions of the Blade, and it's magical powers (Eldritch Knight), but loses it's own abilities, yet retains the host body's attributes.

If the Blade has an active host when cast again, the host will regain control of their body or will return to a soulless state, depending on the state of the host before the spell was cast.