A dragon brought back before the brink of unlife by means not native to the Forgotten Realms. Wraith dragons are neither truly living or truly dead. Killing one can be tricky, as the can reconstitute themselves near their philactories, which could have been created intentionally, or by accident.
Creatures of foreign shadow, their independence of the draconic and undead gods make them unpredictable.
Legendary Resistance (3/day). If the wraith dragon fails a saving throw, it can choose to succeed instead.
Magic Resistance. The dracolich has advantage on saving throws against spells and other magical effects.
Living Shadow. While in dim light or darkness, the dragon has resistance to damage that isn't force, psychic or radiant.
Shadow Stealth. While in dim light or darkness, the dragon can take the hide action as a bonus action.
Sunlight Sensitivity. While in sunlight, the dragon has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.
Multiattack. The dragon makes three attacks: one with its bite and two with its claws.
Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) piercing damage plus 3 (1d6) necrotic damage.
Claw. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage.
Tail. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 15 (2d8 +6) bludgeoning damage.
Shadow Breath (Recharge 5-6). The dragon exhales shadowy fire in a 30-foot cone. Each creature in that area must make a DC 18 Dexterity saving throw, taking 56 (16d6) necrotic damage on a failed save, or half as much damage on a succesful one. A humanoid reduced to 0 hit points by this damage dies, and an undead shadow rises from its corpse and acts immediatly after the dragon in the initiative count. The shadow is under the dragon's control.
The wraith dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dracolich regains spent legendary actions at the start of its turn.
Detect. The dragon makes a Wisdom (Perception) check.
Tail Attack. The wraith dragon makes a tail attack.
Possession. The wraith dragon attempts to take over a creature's body. The target creature must be within sight and must make a DC 18 Wisdom saving throw or be possessed. Undead creatures must make their Wisdom saving throw with disadvantage. Possession ends when the dragon chooses to end it, if Banished is cast on the host creature or if the creature dies.