Dark Smite

The next time you hit a creature with a weapon attack before this spell ends, the weapon gleams with demonic darkness as you strike. The attack deals an extra 2d6 necrotic damage to the target and gains temporary hit points equal to the necrotic damage that’s been dealt. 

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the extra damage increases by 1d6 for each slot level above 2nd