Amphibious. The dragon can breathe air and water.

Legendary Resistance (3/Day, or 4/Day in Lair). If the dragon fails a saving throw, it can choose to succeed instead.

Multiattack. The dragon makes three Rend attacks. It can replace one attack with a use of Spellcasting to cast Vicious mockery (level 3 version).

Rend. Melee Attack Roll: +11, reach 10 ft. Hit: 13 (2d6 + 6) Slashing damage plus 4 (1d8) Acid

Fire breath (Recharge 5–6). Dexterity Saving Throw: DC 18, each creature in a 40-foot-long, 10-foot-wide Line. Failure: 60 (12d10) Fire damage. Success: Half damage.

Spellcasting. The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 17, +9 to hit with spell attacks):

At Will: Detect Magic, Fear, Vicious mockery (level 3 version, he calls you a gerbil)

1/Day Each: Misty step

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn , the dragon can expend a use to take one of the following actions. The dragon regains all expended uses at the start of each its turns.

Frightful Presence. The dragon uses Spellcasting to cast Fear. The dragon can’t take this action again until the start of its next turn.

Pounce. The dragon can move up to half its Speed, and it makes one Rend attack.