Chromatic Awakening (Recharges after a Short or Long Rest). If the greatwyrm would be reduced to 0 hit points, its current hit point total instead resets to 425 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 XP total) for defeating the greatwyrm after its Chromatic Awakening activates.

Chromatic Affinity. The greatwyrm is immune to damage corresponding to its chromatic type*.

* Acid (Black); cold (White); fire (Red); lightning (Blue); poison (Green).

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.

Dragonsight Tethers. The greatwyrm was formed from the merging of the dragon's many echoes across the multiverse. Thus, when the greatwyrm would die, it is instead banished from its current universe into a different one, from which one of its original echoes hailed from, and regains all of its hitpoints. It cannot return to the universe it was banished from for (5d20) years, and its challenge rating and stats are reduced by 1. If the greatwyrm's CR ever reaches 25, it can no longer benefit from this trait.

Multiattack. The greatwyrm makes one Bite attack and two Claw attacks.

Bite. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) piercing damage plus 13 (2d12) force damage. Additionally, one of the following effects occurs, determined by the greatwyrm's chromatic type:

Black. The target must succeed on a DC 26 Dexterity saving throw or have its AC reduced by 2 until the start of the greatwyrm's next turn.

Blue. The target must succeed on a DC 26 Constitution saving throw or it is stunned until the start of the greatwyrm’s next turn.

Green. The target must succeed on a DC 26 Constitution saving throw or it is poisoned until the start of the greatwyrm’s next turn.

Red. The target must succeed on a DC 26 Dexterity saving throw or start burning, taking (2d6) fire damage at the start of its turns. It or another creature can use an action to put out the flames.

White. The next attack that hits the greatwyrm deals (2d10) cold damage back to the attacker.

Claw. Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: 19 (2d8 + 10) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 20) and is restrained until this grapple ends. The greatwyrm can have only one creature grappled this way at a time.

Tail. Melee Weapon Attack: +18 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.

Breath Weapon (Recharge 5–6). The greatwyrm exhales a blast of energy in a 300-foot cone. Each creature in that area must make a DC 26 Dexterity saving throw. On a failed save, the creature takes 78 (12d12) damage from the dragon's chromatic type*. On a successful save, the creature takes half as much damage.

* Acid (Black); cold (White); fire (Red); lightning (Blue); poison (Green).

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

Attack. The greatwyrm makes one Claw or Tail attack.

Wing Attack (Costs 2 Actions). The greatwyrm beats its wings. Each creature within 30 feet of it must succeed on a DC 26 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 four 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 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) damage from the dragon's chromatic type*.

* Acid (Black); cold (White); fire (Red); lightning (Blue); poison (Green).

Elemental Surge. (Costs 3 Actions; Recharges 4-6). The greatwyrm unleashes the elemental energy manifesting across its body, generating a cataclysm to a range of 100 feet of itself. All creatures in the area must make a DC 26 Dexterity saving throw, and the following effect takes place, depending on the dragon's chromatic type:

Black. On a failed save, targets take 33 (5d12) acid damage. On a successful save, they take half of that damage instead. The area affected then becomes an acidic swamp for the next minute, and all creatures within it have their AC reduced by 3 and gain disadvantage on Constitution and Dexterity saving throws, except for the greatwyrm itself.

Blue. On a failed save, targets take 33 (5d12) lightning damage. On a successful save, they take half of that damage instead. The area affected then becomes a darkened landscape with constant lightning strikes for the next minute, forcing all creatures within to make a DC 20 Dexterity saving throw at the start of their turns, except for the greatwyrm itself. On a failed save, they are stunned until the end of that turn.

Green. On a failed save, targets take 33 (5d12) poison damage. On a successful save, they take half of that damage instead. The area affected then becomes a poisonous jungle for the next minute, and all creatures within it are considered poisoned while they remain there, except for the greatwyrm itself. At the start of their turns, each creature poisoned this way must make a DC 20 Constitution saving throw. On a failed roll, they gain 1 level of exhaustion, up to a maximum of 4 to be gained this way.

Red. On a failed save, targets take 33 (5d12) fire damage. On a successful save, they take half of that damage instead. The area affected then becomes an active volcanic field for the next minute, and the ground becomes filled with a 3 foot deep pool of lava, except for a cross-shaped path at its diameter. Any creature within the area but not inside the lava takes (3d8) fire damage at the start of its turns, and any creature that starts its turn inside the lava takes (18d10) fire damage.

White. On a failed save, targets take 33 (5d12) cold damage. On a successful save, they take half of that damage instead. The area affected then becomes a frigid wasteland, and all creatures starting their turns in it must make a DC 20 Constitution saving throw, except for the greatwyrm itself. On a failed save, they fall prone and have their speeds reduced to 0 until the end of the greatwyrm's next turn. If a creature has its speed reduced to 0 in this way for three consecutive turns, it is frozen solid and is considered paralyzed until the area goes back to normal or it is removed from the area.