Amphibious. Zor'onath can breathe air and water.

Legendary Resistance (3/Day). If Zor'onath fails a saving throw, it can choose to succeed instead.

Living Shadow. While in dim light or darkness, Zor'onath has resistance to damage that isn’t force, psychic, or radiant.

Shadow Stealth. While in dim light or darkness, Zor'onath can take the Hide action as a bonus action.

Magic Resistance. Zor'onath has advantage on saving throws against spells and other magical effects.

Magic Weapons. Zor'onath’s weapon attacks are magical.

Regeneration. Zor'onath regains 15 hit points at the start of its turn. If it takes radiant damage, this trait doesn’t function at the start of its next turn. Zor’onath dies only if it starts its turn with 0 hit points and doesn’t regenerate.

Draining Shade (Mythic Trait; Recharges after a Short or Long Rest). If Zor'onath is reduced to 0 hit points and he doesn't regenerate hit points, he doesn't die or fall unconscious. Instead he regains hit points equal to his hit point maximum. In addition, every living creature within 100 feet of Zor'onath takes 2d10 necrotic damage and he gains temporary hit points equal to the total damage dealt.

Multiattack. Zor'onath can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 23 (2d12 + 10) piercing damage plus 10 (3d6) necrotic damage plus 10 (3d6) poison damage.

Claw. Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: 28 (4d8 + 10) slashing damage.

Tail. Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: 21 (2d10 + 10) bludgeoning damage.

Frightful Presence. Each creature of Zor'onath's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 23 Wisdom saving throw or become 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 is immune to the dragon's Frightful Presence for the next 24 hours.

Poison Breath (Recharge 5–6). Zor'onath exhales poisonous gas in a 90-­-foot cone. Each creature in that area must make a DC 23 Constitution saving throw, taking 91 (26d6) poison damage and be poisoned for one hour on a failed save, or half as much damage on a successful one.

Shadow Breath (Recharge 5–6). Zor'onath exhales thick, black shadow in a 90-­-foot cone. Each creature in that area must make a DC 23 Constitution saving throw, taking 77 (14d10) necrotic damage on a failed save and one level of exhaustion, or half as much damage on a successful one.

Zor'onath 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. Zor'onath regains spent legendary actions at the start of its turn.

Detect. Zor'onath makes a Wisdom (Perception) check.

Tail Attack. Zor'onath makes a tail attack.

Wing Attack (Costs 2 Actions). Zor'onath beats its wings. Each creature within 15 feet of the dragon must succeed on a DC 23 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. Zor'onath can then fly up to half its flying speed.

Noxious Shadow (Costs 3 Actions). Zor’onath radiates black gas around it. Each creature within 25 feet of the dragon must make a DC 23 Constitution saving throw or take 11 (2d10) necrotic damage and 11 (2d10) poison damage and can’t regain hit points until the end of their next turn. They take half damage on a success and  don’t suffer any additional effects.

If Zor'onath’s mythic trait is active, he can use the options below as legendary actions for 1 hour after using Draining Shade.

Noxious Shadow (Costs 1 Actions). Zor’onath radiates black gas around it. Each creature within 25 feet of the dragon must make a DC 23 Constitution saving throw or take 11 (2d10) necrotic damage and 11 (2d10) poison damage and can’t regain hit points until the end of their next turn. They take half damage on a success and  don’t suffer any additional effects.

Shade Breath (Costs 2 Actions). Zor'onath exhales thick, black shadow in a 60-­-foot cone. Each creature in that area must make a DC 23 Constitution saving throw, taking 34 (7d10) necrotic damage on a failed save and have their hit point maximum reduced by half the damage taken, or half as much damage on a successful one and don't suffer any additional effects.