Multiple Heads. The dragon has three heads of red, white, and green dragons. While it has more than one head, the dragon has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Reactive Heads. For each head the dragon has beyond one, it gets an extra reaction that can be used only for opportunity attacks.

Multiattack. The dragon makes three attacks with its bite. The Dragon may instead use two of its breath weapons on the same turn, but can only use one of its reactions until it's following turn.

Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 16 (2d10 + 5) piercing damage plus 4 (1d8) fire, poison, or cold damage. Only one of each damage type can be dealt on its multiattack.

Breath Weapons(Recharge 6).

Cold Breath. The dragon exhales an icy blast in a 30-foot cone. Each creature in that area must make a DC 17 Constitution saving throw, taking 31 (7d8) cold damage on a failed save, or half as much damage on a successful one.

Poison Breath. The dragon exhales poisonous gas in a 30-foot cone. Each creature in that area must make a DC 17 Constitution saving throw, taking 31 (9d6) poison damage on a failed save, or half as much damage on a successful one.

Fire Breath . The dragon exhales fire in a 30-foot cone. Each creature in that area must make a DC 17 Dexterity saving throw, taking 42 (12d6) fire damage on a failed save, or half as much damage on a successful one.