You summon a shadowy version of your weapon that will grow stronger and more visible when you hit enemies gathering power that you can release in 1 attack. When the shadow weapon is released it will strike at a nearby enemy after which it will disappear.
Once released, the shadow weapon will deal 1d4 plus 1d4 per hit you have registered on any target while the spell has been active.
The Duration is concentration, but the shadow weapon will become harder to maintain the more powerful it gets (getting a +1 to concentration per round.)