Waking Nightmare

The warlock performs a ritual using a sprig of corpseweed and 100 GP of gems while the target is in view. When the ritual ends, the target must succeed on a DC 20 Charisma saving throw or be enchanted. On a failed save, the target seems unaffected until they next fall asleep within a period of 24 hours. Through their sleep, the target is wracked with terrible nightmares, and when they awaken, the danger of their nightmare carries over into real life. The nightmare entity (at the DM's discretion) can only be seen by the target, and may attack only the target. Half of the hit points taken by this entity become temporarily unavailable.

The spell lasts until dispelled, the entity is killed, the target dies, or 24 hours have passed since the spell was cast.