Amphibious. The chromatic abomination can breathe air and water.

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

Multiple Heads. The chromatic abomination has two heads. While it has more than one head, the chromatic abomination has advantage on saving throws against being blinded, charmed, frightened, stunned, and knocked unconscious.

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

Wakeful. While the chromatic abomination sleeps, the other head is awake.

Multiattack. The chromatic abomination can use its Frightful Presence. It then makes four attacks: two with its bite and two with its claws.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 18 (2d10 + 8) piercing damage plus 6 (2d6) acid or fire damage (its choice).

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

Tail. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 16 (2d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of the chromatic abomination's choice that is within 120 feet of the chromatic abomination and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the chromatic abomination's Frightful Presence for the next 24 hours.

Acid Breath (Recharge 5-6). The chromatic abomination exhales acid in a 60-foot line that is 5 feet wide. Each creature in that line must make a DC 21 Dexterity saving throw, taking 48 (12d8) acid damage on a failed save, or half as much damage on a successful one.

Fire Breath (Recharge 5-6). The chromatic abomination exhales fire in a 60-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 54 (18d6) fire damage on a failed save, or half as much on a successful one.

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

Detect. The chromatic abomination makes a Wisdom (Perception) check.

Tail Attack. The chromatic abomination makes a tail attack.

Wing Attack (Costs 2 Actions). The chromatic abomination beats its wings. Each creature within 10 feet of the chromatic abomination must succeed on a DC 22 Dexterity saving throw or take 14 (2d6 + 8) bludgeoning damage and be knocked prone. The chromatic abomination can then fly up to half its flying speed.