Enfeebling Blow

From Kronopolis and the Flat Plane

"Using necromantic magic, ghostly energy surrounds the target."

Tier 1 You may make an attack action. On a hit, the target is prevented from regaining hit points until the start of its turn.
Tier 2 + 1d6 necrotic damage.

The target must make a contested Constitution (Brawn) check. On a failure, the damage of the creature's attacks is halved until the start of your next turn.

Tier 3 + 1d6 necrotic damage.

On a failure, the creature has disadvantage on Strength, Dexterity, Constitution and Perception ability checks, as well as attack rolls until the start of your next turn.