Ancient Copper Dragon
Gargantuan Dragon (metallic), Chaotic GoodAC 21
HP 367 (21d20 + 147)
Speed 40 ft., climb 40 ft., fly 80 ft.
STR
27 (+8)
Save +8
DEX
12 (+1)
Save +8
CON
25 (+7)
Save +7
INT
20 (+5)
Save +5
WIS
17 (+3)
Save +10
CHA
22 (+6)
Save +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
Traits
Legendary Resistance (4/Day, or 5/Day in Lair). If the dragon fails a saving throw, it can choose to succeed instead.
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+). dex 22, each creature in an 90-foot-long, 10-foot-wide Line. Failure: 63 (14d8) Acid damage. Success: Half damage.
Slowing Breath. con 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
Giggling Magic. cha 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.