Ancient Copper Dragon

From Monster Manual, page 110.

**Hit Points:** 350 (20d20 + 140)
 **STR**
27 (+8)
12 (+1)
25 (+7)
20 (+5)
17 (+3)
 **Saving Throws:** Dex +8, Con +14, Wis +10, Cha +11
**Skills:** Deception +11, Perception +17, Stealth +8
**Damage Immunities:** acid
**Senses:** blindsight 60 ft., darkvision 120 ft., passive Perception 27
**Languages:** Common, Draconic
 ***Legendary Resistance (3/Day).*** If the dragon fails a saving throw, it can choose to succeed instead.
 ***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:* +15 to hit, reach 15 ft., one target. *Hit:* 19 (2d10 + 8) piercing damage.
***Claw.** Melee Weapon Attack:* +15 to hit, reach 10 ft., one target. *Hit:* 15 (2d6 + 8) slashing damage.
***Tail.** Melee Weapon Attack:* +15 to hit, reach 20 ft., one target. *Hit:* 17 (2d8 + 8) bludgeoning 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.
***Breath Weapons (Recharge 5-6).*** The dragon uses one of the following breath weapons:
* **Acid Breath.** The dragon exhales acid in a 90-foot line that is 10 feet 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 dragon exhales gas in a 90-foot cone. 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.

***Change Shape.*** The 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 dragon's choice).
 The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action 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.
 On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects; the dragon can't use the same effect two rounds in a row:
* The dragon chooses a point on the ground that it can see within 120 feet of it. Stone spikes sprout from the ground in a 20-foot radius centered on that point. The effect is otherwise identical to the spike growth spell and lasts until the dragon uses this lair action again or until the dragon dies.
 The region surrounding a legendary copper dragon's lair is warped by the dragon's magic, which creates one or more of the following effects:
* Magic carvings of the dragon's smiling visage can be seen worked into stone terrain and objects within 6 miles of the dragon's lair.
* Tiny beasts such as rodents and birds that are normally unable to speak gain the magical ability to speak and understand Draconic while within 1 mile of the dragon's lair. These creatures speak well of the dragon, but can't divulge its whereabouts.
* Intelligent creatures within 1 mile of the dragon's lair are prone to fits of giggling. Even serious matters suddenly seem amusing.

If the dragon dies, the magic carvings fade over the course of 1d10 days. The other effects end immediately.