Ancient Copper Dragon

Gargantuan Dragon (Metallic), Chaotic Good

AC: 21

Initiative: +15 (25)

HP: 367 (21d20 + 147)

Speed: 40 ft., climb 40 ft., fly 80 ft.

STR: 27 (+8)
DEX: 12 (+1)
CON: 25 (+7)
INT: 20 (+5)
WIS: 17 (+3)
CHA: 22 (+6)

Saving Throws: Dex +8, Wis +10

Skills: Deception +13, Perception +17, Stealth +8

Immunities: acid

Senses: Blindsight 60 ft., Darkvision 120 ft., Passive Perception 27

Languages: Common, Draconic

CR: 21 (XP 33,000, or 41,000 in lair; PB +7)

Habitat: Hill

Treasure: Arcana

Legendary Resistance (4/Day, or 5/Day in Lair).

If the dragon fails a saving throw, it can choose to succeed instead.

Spellcasting.

The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 21):

At will: Detect Magic, Mind Spike (level 5 version), Minor Illusion, Shapechange (Beast or Humanoid form only, no Temporary Hit Points gained from the spell, and no Concentration or Temporary Hit Points required to maintain the spell)

1/day each: Greater Restoration, Major Image, Project Image

Actions

Multiattack.

The dragon makes three Rend attacks. It can replace one attack with a use of (A) Slowing Breath or (B) Spellcasting to cast Mind Spike (level 5 version).

Rend.

Melee Attack Roll: +15, reach 15 ft. Hit: 19 (2d10 + 8) Slashing damage plus 9 (2d8) Acid damage.

Acid Breath (Recharge 5-6).

Dexterity Saving Throw: DC 22, each creature in an 90-foot-long, 10-foot-wide Line. Failure: 63 (14d8) Acid damage. Success: Half damage.

Slowing Breath.

Constitution Saving Throw: DC 22, each creature in a 90-foot Cone. Failure: The target can't take Reactions; its Speed is halved; and it can take either an action or a Bonus Action on its turn, not both. This effect lasts until the end of its next turn.

Legendary Actions

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn, this creature can expend a use to take one of the following actions; it regains all expended uses at the start of each of its turns.

Giggling Magic.

Charisma Saving Throw: DC 21, one creature the dragon can see within 120 feet. Failure: 31 (9d6) Psychic damage. Until the end of its next turn, the target rolls 1d8 whenever it makes an ability check or attack roll and subtracts the number rolled from the D20 Test. Failure or Success: The dragon can't take this action again until the start of its next turn.

Mind Jolt.

The dragon uses Spellcasting to cast Mind Spike (level 5 version). The dragon can't take this action again until the start of its next turn.

Pounce.

The dragon moves up to half its Speed, and it makes one Rend attack.

Regional Effects

The region containing an adult or ancient copper dragon's lair is changed by its presence, creating the following effects:

Chatty Critters.
Tiny Beasts magically gain the ability to speak and understand Draconic while within 6 miles of the lair.
Giggle Fits.
Whenever a creature other than the dragon and its allies is within 1 mile of the lair and rolls a 1 on a D20 Test, it must succeed on a DC 15 Wisdom saving throw or have the Incapacitated condition until the end of its next turn, as it is wracked with laughter.

If the dragon dies or moves its lair elsewhere, these effects end immediately.

Find this creature in the encounter builder

Source: Monster Manual (2025), p. 80 - Licenses and attribution