Ancient Copper Dragon

Flow Within the Mountain. The dragon has advantage on Stealth checks made to hide in mountainous regions. By spending 1 minute in concentration while touching a natural stone surface, the dragon can magically merge into it and emerge from any connected stone surface within a mile.

Legendary Resistance (3/Day). When the dragon fails a saving throw, it can choose to succeed instead. When it does, some of its scales fall away and turn to stone. If it has no more uses of this ability, its Armor Class is reduced to 19 until it finishes a long rest.

Innate Spellcasting. The dragons spellcasting ability is Charisma (save DC 19). It can innately cast the following spells, requiring no material components. 3/day each:hideous laughter, suggestion, mislead, polymorph, 1/day:irresistible dance, mass suggestion

Multiattack. The dragon attacks with its bite and twice with its claws. In place of its bite it can use Acid Spit.

Bite. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 30 (4d10 + 8) piercing damage plus 9 (2d8) acid damage.

Claws. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) slashing damage.

Tail. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 21 (3d8 + 8) bludgeoning damage and the dragon pushes the target 10 feet away.

War Pick (Humanoid Form Only). Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 12 (1d8 + 8) piercing damage.

Acid Spit. The dragon targets a creature within 60 feet forcing it to make a DC 22 Dexterity saving throw. The creature takes 22 (4d10) acid damage on a failure or half damage on a success. A creature that fails the save also takes 11 (2d10) ongoing acid damage. A creature can use an action to end the ongoing damage.

Breath Weapons (Recharge 5-6). The dragon uses one of the following breath weapons:

Acid Breath. The dragon spits acid in a 90-foot-long 10-foot-wide line. Each creature in the area makes a DC 22 Dexterity saving throw taking 85 (19d8) acid damage on a failed save or half damage on a success. A creature that fails the save is blinded until the end of its next turn.

Slowing Breath. The dragon exhales toxic gas in a 90-foot cone. Each creature in the area makes a DC 22 Constitution saving throw becoming slowed for 1 minute on a failure. A creature repeats the saving throw at the end of each of its turns ending the effect on itself on a success.

Change Shape. The dragon magically takes the shape of a humanoid or beast, or changes 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 (dragons choice). In the new form, the dragons stats are unchanged except for its size. It can't use Acid Spit, Breath Weapons, Tail Attack, or Wing Attack except in dragon form. In beast form, it can attack only with its bite and claws, if appropriate to its form. If the beast form is Large or smaller, the reach of these attacks is reduced to 5 feet. In humanoid form, it can attack only with its war pick.

Tail Attack. When a creature the dragon can see within 10 feet hits the dragon with a melee attack, the dragon makes a tail attack against it.

The dragon can take 3 legendary actions. Only one legendary action can be used at a time and only at the end of another creatures turn. It regains spent legendary actions at the start of its turn.

Roar. Each creature of the dragons choice within 120 feet that can hear it makes a DC 19 Charisma saving throw. On a failure, it is frightened for 1 minute. A creature repeats the saving throw at the end of its turns, ending the effect on itself on a success. When it succeeds on a saving throw or the effect ends for it, it is immune to Roar for 24 hours.

Wing Attack. The dragon beats its wings. Each creature within 15 feet makes a DC 23 Dexterity saving throw. On a failure, it is pushed 10 feet away and knocked prone. The dragon can then fly up to half its fly speed.

Tricksters Gambit (Costs 2 Actions). The dragon magically teleports to an unoccupied space it can see within 30 feet and creates two illusory duplicates in different unoccupied spaces within 30 feet. These duplicates have an AC of 11, and a creature that hits one with an attack can make a DC 19 Intelligence (Investigation) check, identifying it as a fake on a success. The duplicates disappear at the end of the dragons next turn but otherwise mimic the dragons actions perfectly, even moving according to the dragons will.