Void Burn

You summon a void tendril to slash at a creature that you can see within range. The target must make a Constitution saving throw. On a failed save, a blackish purple burn appears where they were struck and it takes 14d6 necrotic damage, or half as much damage on a successful save. The damage can't reduce the target's hit points below 1. If the target fails the saving throw, its hit point maximum is reduced for 1 hour by an amount equal to the necrotic damage it took.