Hex of Weakness

8th-level Necromancy
Casting Time: 1 action
Range: 150 feet
Components: VSM (a fracture-ridden bone)
Duration: Instantaneous

You wrack the body of a creature that you can see within range with agonizing pain and fatigue, attempting to crush its body and soul. The target takes 4d6 shadow damage and must make a Constitution saving throw.
On a failed save, the creature's Strength, Dexterity and Constitution scores become 1. This adjustment to Strength and Dexterity can penalize attack and damage rolls, Dexterity can affect armor class, and Constitution affects maximum hit points, granting a penalty to maximum hit points equal to the change in Constitution modifier times your number of hit die.
At the end of every 30 days, the creature can repeat its saving throw against this spell. If it succeeds on its saving throw, the spell ends.
The spell can also be ended by greater restoration, heal, or wish.
At Higher Levels. When you cast this spell using a spell slot of 9th level or higher, you can target an additional creature for each slot level above 8th.

Source: Homebrew