Keen Smell. The dragon has advantage on Wisdom (Perception) checks that rely on smell.

 Magic Resistance. The dragon has advantage on saving throws against spells and other magical effects.

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

Charge. If the dragon moves at least 10 feet straight toward a target and then hits it with a gore attack on the same turn, the target takes an extra 16 (3d10) piercing damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be pushed up to 10 feet away and knocked prone.

Multiattack. The dragon can use its Frightful Presence. The dragon makes three attacks: one with its bite and two with its claws. Alternatively the dragon can replace one of it's bite attacks with a gore attack.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 20 (2d10 + 9) piercing damage.

Claw. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 16 (2d6 + 9) slashing damage.

Gore. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 21 (2d12 + 9) piercing damage.

Tail. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 18 (2d8 + 9) piercing 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 16 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.

 Galvanice Breath (Recharge 5–6). The dragon exhales a 60-foot cone composed of icy hail and crackling electricity. Each creature in that area must make a DC 20 Dexterity saving throw, taking 33 (6d10) cold damage and taking 33 (6d10) lightning damage on a failed save, or half as much damage on a successful one.

Innate Spellcasting. The dragon casts one of the following spells, requiring no spell components and using Charisma as the spellcasting ability (spell save DC 18):

2/day: jump (self only)

Alternate Form. The dragon magically polymorphs into a beast or monstrosity that is of large size or smaller, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).

In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

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 19 Dexterity saving throw or take 16 (2d6 + 9) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.