Blood-Siphon Blade

You brandish the weapon used in the spell's casting and make a melee attack with it against one creature (that can bleed) within 5 feet of you. On a hit, the target suffers the weapon attack's normal effects and then a vile siphoning energy attacks its body, taking necrotic damage equal to your spellcasting modifier and you regain hit points equal to the necrotic damage dealt from this spell.

This spell's damage increases when you reach certain levels. At 5th level, the melee attack deals an extra 1d4 necrotic damage to the target on a hit. The damage roll increase by 1d4 at 11th level (2d4) and again at 17th level (3d4).