Darastrien's Shadow Blight

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

A greater restoration spell cast with a 9th level spell slot or a wish spell can end the effect on an affected creature.

Constructs and undead are unaffected by this spell.