Amphibious. The dragon can breathe air and water.

Regeneration. The dragon heals 15 HP at the start of each of it's turns as long as it has at least 1 HP remaining.

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

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

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 19 (2d10 + 8) piercing damage.

Claw. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 8) slashing damage.

Tail. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 21 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.

Breath Weapons (Recharge 5–6). The dragon uses one of the following breath weapons.

Chaos Breath. The dragon creates a shining bead of chaotic force in its mouth, then releases the energy in a 60-foot cone. Each creature in that area must make a DC 21 Strength saving throw. On a failed save, the creature takes 45 (10d8) force damage, and its speed becomes 0 until the start of the dragon’s next turn. On a successful save, the creature takes half as much damage, and its speed isn’t reduced.

Darkness Breath. The dragon shoots a ball of magic out of its mouth that reaches 60 feet. Each creature in that area must make a DC 21 Dexterity saving throw, taking 55 (10d10) necrotic damage on a failed save, or half as much damage on a successful one. The 15 foot area around where the ball of magic hit now has lingering 55 (10d10) with a DC 21 Constitution Saving throw for anyone who steps in it dealing the same damage. The necrotic area lasts for 3 turns.

Starlight Breath. The dragon exhales a flashing mote of radiant energy that travels to a point the dragon can see within 180 feet of itself, then blossoms into a 30-foot-radius sphere centered on that point. Each creature in the sphere must make a DC 21 Constitution saving throw, taking 55 (10d10) radiant damage on a failed save, or half as much damage on a successful one.

Weakening Breath. The dragon exhales gas in a 60-foot cone. Each creature in that area must succeed on a DC 21 Strength saving throw or have disadvantage on Strength-based attack rolls, Strength checks, and Strength saving throws 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.

Slowing Breath. The dragon exhales gas in a 60-foot cone. Each creature in that area must succeed on a DC 21 Constitution saving throw. On a failed save, the creature can't use reactions, its speed is halved, and it can't make more than one attack on its turn. In addition, the creature can use either an action or a bonus action on its turn, but not both. These effects last for 1 minute. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself with a successful save.

Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).

In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

The 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 dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 22 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.