Blood Blade

You create a glistening sword of blood in your hand. The magic sword lasts until the spell ends. It counts as a simple melee weapon, with which you are proficient. It deals 1d8 slashing damage and 1d8 necrotic damage on hit, and has the finesse and light property.

If you make an attack against a bloodied creature (one that has half of less of its maximum hit points), the attack roll gains advantage. The first time during the duration you land a critical hit with the weapon, you regain the hit points expended to cast it. The weapon disperses into red mist and the spell ends of you drop or let go the sword.

At higher levels. When you cast this spell using a 3rd- or 4th-level spell slot, necrotic damgae it deals increases by 1d8 (to 2d8). When you cast it using a 5th- or 6th-level spell slot, the necrotic damage increases to 3d8. When you cast it using a spell slot of 7th level or higher, the necrotic damage increases to 4d8.