Black Wraith

Daylight Sensitivity. If the wraith has disadvantage on all attack rolls and saving throws while in sunlight.

Bound to Dark Duty. The wraith is neither living nor dead, but is of both worlds. It can simultaneously perceive and effect the material plane and the ethereal plane.

If the wraith is reduced to 0 hit points, it isn't killed but is banished without form to the ethereal plane instead. It reforms without weapons or armour in the nearest place of evil after 1d10 days.

Fear Aura. Any creature hostile to the wraith that starts its turn within 60 feet of the wraith must make a DC 15 Wisdom saving throw, unless the wraith is incapacitated. On a failed save, the creature is frightened until the start of its next turn. If a creature's saving throw is successful, the creature is immune to the wraith's Fear Aura for the next 24 hours.

Magic Resistance. The wraith has advantage on saving throws against spells and other magical effects, and is immune to any spell or effect that would alter its form.

Multiattack. The wraith makes two attacks with its longsword.

Longsword. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) slashing damage, or 8 (1d10 + 3) slashing damage if used with two hands.

Piercing Screech (recharge 5-6). The wraith emits a soul-piercing screech that saps the resolve of creatures who hear it. Each creature of the wraith's choice that is able to hear the wraith must succeed on a DC 15 Wisdom saving throw or become incapacitated until the end of their next turn, and are frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature has advantage on subsequent saving throws against the wraith's Piercing Screech for the next 24 hours.