Legendary Resistance (4/Day). If the greatwyrm fails a saving throw, it can choose to succeed instead.

Unusual Nature. The greatwyrm doesn't require food or drink.

Chromatic Awakening (Recharges After a Short or Long Rest). If the greatwyrm would be reduced to 0 hit points, iits current hit point total resets to 530 hit points, it recharges its Breath Weapon, and it regains any expended uses of Legendary Resistance. Additionally, the greatwyrm can now use the options in the "Mythic Actions" section for 1 hour. Award a party an additional 120,000 XP (240,000 total) for defeating the greatwyrm after its Chromatic Awakening activates.

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

Bite. Melee Weapon Attack: +28 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) piercing damage plus an additional 14 (4d6) fire damage.

Claw. Melee Weapon Attack: +28 to hit, reach 10 ft., one target. Hit: 17 (2d6 + 10) slashing damage. If the target is a Huge or smaller creature, it is [condition]grappled[/condition (escape DC 20) and is restrained until this grapple ends. The greatwyrm can only have one creature grappled this way at a time.

Tail. Melee Weapon Attack: +28 to hit, reach 20 ft., one target. Hit: 19 (2d8 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 26 Strength saving throw or be knocked prone.

Frightful Presence. Each creature of the greatwyrm's choice that is within 120 feet of the greatwyrm 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 greatwyrm’s Frightful Presence for the next 24 hours.

Breath Weapon. The greatwyrm uses one of the following breath weapons:

Fire Breath (Recharge 5–6). The greatwyrm exhales fire in a 300-foot cone. Each creature in that area must make a DC 26 Dexterity saving throw, taking 91 (26d6) fire damage on a failed save, or half as much damage on a successful one.

Sapping Breath (Recharge 5-6). The greatwyrm exhales poisonous gas in a 300-foot cone. Each creature in that area must make a DC 25 Constitution saving throw. On a failed save, the creature falls unconscious for 1 minute. On a successful save, the creature becomes poisoned has disadvantage on attack rolls and saving throws until the end of the greatwyrm's next turn. An unconscious creature can repeat the saving throw on the end of each of its turns, ending the effect on itself on a success.

Shapechange. The greatwyrm magically transforms into any creature that is Medium or Small, while retaining its game statistics (other than its size). This transformation ends if the greatwyrm drops to 0 hit points or uses its action to end it.

The greatwyrm can take 4 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 greatwyrm regains spent legendary actions at the start of its turn.

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

Attack. The dragon makes one Claw or Tail attack.

Wing Attack (Costs 2 Actions). The greatwyrm beats its wings. Each creature within 15 feet of the greatwyrm must succeed on a DC 25 Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. The greatwyrm can then fly up to half its flying speed.

Arcane Spear (Costs 3 Actions). The greatwyrm creates ten spears of magical force. Each spear hits a creature of the greatwyrm's choice it can see within 120 feet of it, dealing 12 (1d8 + 8) force damage to its target, then disappears.

If the greatwyrm's Chromatic Awakening trait has been activated in the last hour, it can use the options below as legendary actions.

Bite. The greatwyrm makes one Bite attack.

Chromatic Flare (Costs 2 Actions). The greatwyrm flares with elemental energy. Each creature in a 60-foot-radius sphere centered on the greatwyrm must succeed on a DC 26 Dexterity saving throw or take 22 (5d8) fire damage.

Shattering Roar (Costs 3 Actions). The greatwyrm unleashes a magical roar. Each creature in a 120-foot-radius sphere centered on the greatwyrm must succeed on a DC 26 Constitution saving throw or take 19 (3d12) thunder damage and be incapacitated until the end of its next turn.