Ancient Green Dragon
gargantuan dragon, lawful evil
AC 21
Initiative +1 (11)
HP 402 (23d20 + 161)
Speed 40 ft., Swim 40 ft., Fly 80 ft.
Skills Deception +13, Perception +17, Persuasion +13, Stealth +8
Immunities poison, poisoned
Senses Blindsight 60 ft., Darkvision 120 ft. Passive Perception 27
Languages Common, Draconic
CR 22 (XP 41,000; PB +7)
Amphibious. The dragon can breathe air and water.
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 Spellcasting to cast Mind Spike (level 5 version).
Poison Breath (Recharge 5-6). Constitution Saving Throw: DC 22, each creature in a 90-foot Cone. Failure: 77 (22d6) Poison damage. Success: Half damage.
Rend. Melee Attack Roll: +15, reach 15 ft. 17 (2d8 + 8) Slashing damage plus 10 (3d6) Poison damage.
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 - 1e/Day Each: Geas, Modify Memory
Legendary Actions
Mind Invasion. The dragon uses Spellcasting to cast Mind Spike (level 5 version).
Noxious Miasma. Constitution Saving Throw: DC 21, each creature in a 30-foot-radius Sphere [Area of Effect]|XPHB|Sphere centered on a point the dragon can see within 90 feet. Failure: 17 (5d6) Poison damage, and the target takes a -2 penalty to AC until the end of its next turn. Failure or Success: 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.
Ancient Green Dragon is from the System Reference Document 5.2.1 (“SRD 5.2.1”) by Wizards of the Coast LLC, used under the Creative Commons Attribution 4.0 International License. Full attribution is on the Licenses & Attribution page.