Amphibious. The dragon can breathe air and water.

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.

Innate Spellcasting. The Dragon’s spellcasting ability is Charisma (spell save DC 13, +5 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

1/day each:  blindness/deafness, melf's acid arrow

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

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 15 (2d10 + 4) piercing damage plus 4 (1d8) necrotic damage.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.

Shadow Breath (Recharge 5–6). The dragon exhales shadowy acid in a 30­-foot line that is 5 feet wide. Each creature in that line must make a DC 15 Dexterity saving throw, taking 49 (11d8) 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.