Adult Storm Dragon

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

Storm Aura. The Dragon is sheathed in furious winds.
The Wind aura deflects any projectiles that pass within 10ft of the dragon.
Small or smaller creatures that start their turn within the aura or enter it for the first time on that turn must make a DC 19 Strength saving throw or they can't pass through the wall and are thrown out.
The Wind also disperses fog, smoke and other gases.
The dragon can toggle this aura as a bonus action.

Flyby. The Dragon does not provoke opportunity attacks

Magic Attacks. The Dragon's attacks count as magical

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 19 (2d10 + 8) piercing damage plus 7 (2d6) lightning damage.

Claw. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 8) slashing damage plus 7 (2d6) lightning damage.

Tail. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage plus 7 (2d6) lightning damage.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 19 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 the dragon's Frightful Presence for the next 24 hours.

Crushing Landing. (Recharge 6). If the dragon is flying, it can attempt to land forcefully in a space of its choice, even if that space is occupied by other creatures.
When it does so, its movement speed is reduced to 0 until the end of the turn, and each creature in the dragon's space or within 10 feet of it, other than the dragon itself, must make a DC 21 Dexterity saving throw or take 52 (8d12) bludgeoning damage and be knocked prone.

Lightning Breath (Recharge 6). The The dragon exhales lightning in a 90-foot line that is 5 ft. wide. Each creature in that line must make a DC 21 Dexterity saving throw, taking 63 (18d6) Lightning damage on a failed save, or half as much damage on a successful one.

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

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 22 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.