The target makes a Con saving throw. On a failed saving throw, they take 3d8 necrotic damage and gain one level of exhaustion. On a successful one, they take half damage and gain no levels of exhaustion. 

Creatures immune to necrotic damage are immune to this spell, creatures resistant to necrotic damage make the saving throw with advantage.

This spell cannot bring a creature to Exhaustion Level 6.

Higher level casting scales as such: 6th level: 2 levels of exhaustion. 7th level: 4d8 damage, 3 levels of exhaustion. 8th level: 4 levels of exhaustion. 9th level: 5d8 damage, 5 levels of exhaustion.