Agonizing Smite

The next time you hit a creature with a melee weapon attack before this spell ends, the weapon sends waves of excruciating pain through the creature's body, and the attack deals an extra 5d8 necrotic damage to the target. Additionally, the target must make a Constitution saving throw. On a failed save, it falls prone and takes 1d8 necrotic damage at the start of its next turn. On a successful save, the target takes half as much damage, doesn't fall prone, and does not take additional damage at the start of its next turn.