Adamantine Pommel of the Rightly Ended

This smooth, grey, extremely hard magical pommel affixes itself to the hilt of any sword, replacing the pommel if it already has one. Once per long rest, as a bonus action, the wielder may remove the pommel from the hilt of his weapon and throw it at  an enemy up to 20' as if it were a dagger. (dexterity + proficiency bonus). On a hit, the enemy takes 1d4 damage and is stunned until the end of it's next turn. After hitting or missing, the pommel returns to the swords hilt and reattaches itself.