Death's Imposition

The magic you weave around one living creature makes it believe it has died.  It must succeed a Charisma saving throw, or fall unconscious and take 4d8 necrotic damage.

At the end of each of its turns, the creature can repeat the saving throw.  If the saving throw succeeds, it wakes up and the spell ends. If it fails the save, it takes 4d8 necrotic damage and remains unconscious.  

If the creature remains unconscious but alive for the full duration, it must make a Constitution saving throw (rather than Charisma).  If it fails, it is reduced to 0 hit points and the spell ends.  Otherwise, the spell ends.

The creature instantly awakens once the spell ends.  Creatures immune to being charmed are immune to this spell.