Dariastern's Shadow Blight

 You point your finger at a target you see within range in dim light or darkness, firing a ray of darting shadows at the target. The target must make a Wisdom save, becoming infected with shadow blight for the duration. While infected in this manner, the target's vulnerable to fire and radiant damage, can't regain hit points and takes 20 radiant damage when it starts its turn in bright light. Also, the target's hit point max is reduced by 1d4 for every long rest it finishes.

A greater restoration spell cast at 9th level or a wish spell ends the effect on an affected creature. Constructs or undead aren't affected by this spell.