Amalthea's Ghostlight

Choose a creature that you can see within range. The target must succeed on a Wisdom saving throw or have a ghostly light hover around them. On a successful save, the target isn’t affected, and you can’t use this spell against it again for 24 hours. Each turn this light is active, the target takes 2d4 necrotic damage and suffers from half a point of exhaustion, maxing at 3. At the end of each of its turns, the target can make another Wisdom saving throw. On a success, the spell ends on the target.