Curse of Agony

2nd-level Necromancy
Casting Time: 1 action
Range: 90 feet
Components: VS
Duration: (C) 1 minute

You curse your target with incredible, agonizing pain and discomfort. While cursed in this way, at the beginning of the target's turn, they must make a Wisdom saving throw or suffer shadow damage equal to your proficiency bonus plus your spellcasting modifier, or half as much damage on a successful one. Three successful consecutive saving throws lifts this effect early.
Dispel magic has no effect on this spell, but remove curse or other similar abilities can remove it.
At Higher Levels. When you cast this spell at 3rd level or higher, the damage over time effect increases by your spellcasting modifier for each spell level above 2nd.

Source: Homebrew