Umbral Blade

Weapon (any sword), rare (requires attunement)

An eerie shadowy trail follows this +1 sword as it moves. It has 3 charges that renew each day at dawn. Once per round when you attack with the sword, you may spend 1 charge to convert your shadow into a ghostly doppelganger which attacks alongside you, granting you advantage on your attack roll. In addition, if both of your rolls on this advantage attack resolve to successful hits, the doppelganger erupts in a pillar of eldritch energy, 206 dealing an extra 4d6 cold damage and stunning the target until the start of your next turn.