Harm

Level: 6

Casting Time: 1 action

Range: 60 feet

Duration: Instantaneous

You unleash a virulent disease on a creature that you can see within range. The target must make a Constitution saving throw. On a failed save, 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. Any effect that removes a disease allows a creature's hit point maximum to return to normal before that time passes.

Source: PHB, page 249. Available in the SRD.