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.

Obligatory D&D Beyond Addition. This is here so this entry is not pinged for being too similar to an existing monster.

Multiattack. The dragon makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 16 (2d10 + 5) piercing damage plus 5 (1d10) necrotic damage.

Claw. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage.

Shadow Breath (Recharge 5–6). The dragon exhales black lightning in a 60-foot line that is 5 feet wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 55 (10d10) necrotic damage on a failed save, or half as much damage on a successful one. A humanoid reduced to 0 hit points by this damage dies, and an undead shadow rises from its corpse and acts immediately after the dragon in the initiative count. The shadow is under the dragon’s control.