Ancient Green Dragon
Gargantuan dragon, lawful evil
Armor Class 21 (natural armor)
Hit Points 402 (23d20 + 161)
Speed 40 ft., fly 80 ft., swim 40 ft., climb 20 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, Persuasion +13, Stealth +8
Damage Immunities poison
Condition Immunities poisoned
Senses blindsight 60 ft., darkvision 120 ft., passive Perception 27
Languages Common, Draconic
Challenge 22 (41,000 XP)
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. 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 - **1/Day Each:** Geas, Modify Memory
Spellcasting (CHA, DC 21, +13 to hit)
At Will: Detect Magic, Mind Spike
1/Day Each: Geas, Modify Memory
Attack Summary
Legendary Actions
The ancient green dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The ancient green dragon regains spent legendary actions at the start of its turn.
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.