Decaying Blade

You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5ft of you. On a hit, the target suffers the weapon attack’s normal effects and it can’t regain hit points until the start of your next turn. If you hit an undead target, it also has disadvantage on attack rolls against you until the end of your next turn.

This spell’s damage increases when you reach certain levels. At 5th level, the melee attack deals an extra 1d8 necrotic damage to the target on a hit. The damage roll increases by 1d8 at 11th level (2d8) and again at 17th level (3d8).