Ancient Copper Dragon

3 legendary actions; one at a time at the end of another creature’s turn, regaining spent uses at the start of its turn

3/day. If the ancient copper dragon fails a saving throw, it can choose to succeed instead.

Melee Weapon Attack: +15 to hit, reach 15 ft.. Hit: 19 (2d10 + 8) piercing damage.

Melee Weapon Attack: +15 to hit, reach 10 ft.. Hit: 15 (2d6 + 8) slashing damage.

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

Melee Weapon Attack: +15 to hit, reach 20 ft.. Hit: 17 (2d8 + 8) bludgeoning damage.

Each creature of the ancient copper dragon's choice that is within 120 ft. 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 ancient copper dragon's Frightful Presence for the next 24 hours.

Recharge 5–6. The ancient copper dragon uses one of the following breath weapons.
Acid Breath. The ancient copper dragon exhales acid in an 90-foot line (10 ft. wide). Each creature in that line must make a DC 22 Dexterity saving throw, taking 63 (14d8) acid damage on a failed save, or half as much damage on a successful one.
Slowing Breath. The ancient copper dragon exhales gas in a 90-foot line (10 ft. wide). Each creature in that area must succeed on a DC 22 Constitution saving throw. On a failed save, the creature can't use reactions, its speed is halved, and it can't make more than one attack on its turn. In addition, the creature can use either an action or a bonus action on its turn, but not both. These effects last for 1 minute. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself with a successful save.

The ancient copper dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, 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 ancient copper dragon's choice).
In a new form, the ancient copper 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 ancient copper dragon makes a Wisdom (Perception) check.

The ancient copper dragon makes a tail attack.

Costs 2 legendary actions. The ancient copper dragon beats its wings. Each creature within 15 ft. of the ancient copper dragon must succeed on a DC 23 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. The ancient copper dragon can then fly up to half its flying speed.