Xiivair, Scourge of the Deep

Amphibious. Xiivair can breathe air and water.

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

Freedom of Movement. Xiivair ignores difficult terrain, and magical effects can't reduce its speed or cause it to be restrained. It can spend 5 feet of movement to escape from nonmagical restraints or being grappled.

Multiattack. Xiivair uses its Frightful Presence. It then makes three attacks: one with its bite and two with its claws. 

Frightful Presence. Each creature of Xiivair's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 17 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 Xiivair's Frightful Presence for the next 24 hours.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., 1 target. Hit: 32 (6d8 + 5) Piercing damage. 

Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 7) Slashing damage.

Steam Breath (Recharge 5-6). Xiivair exhales a stream of hot steam in a 120 foot cone. Each creature in the area must make a DC 24 Dexterity saving throw, taking 32 (9d6) cold damage and 32 (9d6) fire damage on a failed save, or half as much on a successful one.

Steam Step (2/Day). When a creature attempts to attack Xiivair, it can choose to teleport up to 30 ft away in a cloud of steam. Any creatures within 5 ft of Xiivair take 9 (2d8) Cold damage and 9 (2d8) Fire damage.