Adult Yellow Dragon

Aerial Superiority. The dragon has Advantage on attack rolls made while using its Flying speed.

Amphibious. The dragon can breathe air and water.

Legendary Resistance (3/Day). 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 Vitriolic Sphere.

Rend. Melee Attack Roll: +10, reach 10 ft. Hit: 16 (2d10 + 5) Slashing damage plus 9 (2d8) Force damage.

Salty Breath (Recharge 5–6). Dexterity Saving Throw: DC 16, each creature in a 60-foot Cone. Failure: 38 (11d6) Force damage, and the target's speed is Restrained by solid salt. A creature can take an action to end the Restrained condition on the target. Success: Half damage only.

Spellcasting. The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 13):

At Will: Control Water, Fog Cloud (level 3 version), Vitriolic Sphere

1/Day: Cloudkill

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 of its turns.

Mist Shaper. The dragon uses Spellcasting to cast Fog Cloud (level 3 version). The dragon can’t take this action again until the start of its next turn.

Time Shaper. The dragon uses Spellcasting to cast Slow. The dragon can’t take this action again until the start of its next turn.

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