Relentless Nightmare

If the nightmare fails a saving throw, it can choose to succeed instead.

If the nightmare dies, its body disappears into mist, and it gains a new body in 1d10 days, reviving with all its Hit Points in the nearest unoccupied space next to an Unconscious creature cursed by its Haunter's Spear. This trait doesn't function if there are no remaining targets cursed in this way.

The nightmare makes two Haunter's Spear attacks. It can replace one attack with a use of Exhausting Gaze.

Melee or Ranged Attack Roll: +9, reach 10 ft. or range 60 ft. Hit: 14 (2d8 + 5) Piercing damage plus 10 (3d6) Psychic damage. Additionally, the target is cursed by the nightmare if it isn't already. Until this curse ends, finishing a Long Rest doesn't reduce the target's Exhaustion level.

Wisdom Saving Throw: DC 16, one creature the nightmare can see within 60 feet. Failure: 14 (4d6) Psychic damage, and the target gains 1 Exhaustion level.

The nightmare teleports to an unoccupied space within 5 feet of a creature it can see, then makes a Haunter's Spear attack.

The nightmare targets one creature it can see within 120 feet that's cursed by its Haunter's Spear. The target takes 7 (2d6) Psychic damage and has the Unconscious condition for 1 hour, until it takes damage, or until a creature within 5 feet of it takes an action to wake it.