Ancient Green Dragon

Gargantuan dragon, lawful evil

Armor Class 21 (natural armor)

Hit Points 385 (22d20 + 154)

Speed 40ft., fly 80ft., swim 40ft.

Saving Throws Dex +8, Con +14, Wis +10, Cha +11

Skills Deception +11, Insight +10, Perception +17, Persuasion +11, Stealth +8

Damage Immunities poison

Condition Immunities poisoned

Senses blindsight 60ft., darkvision 120ft., passive Perception 27

Languages Common, Draconic

Challenge 22 (41,000 XP)

Traits

Amphibious

The dragon can breathe air and water.

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 15ft., one target.
Hit: 19 (2d10+8) piercing damage plus 10 (3d6) poison damage.

Claw

Melee Weapon Attack: +15 to hit, reach 10ft., one target.
Hit: 22 (4d6+8) slashing damage.

Tail

Melee Weapon Attack: +15 to hit, reach 20ft., one target.
Hit: 17 (2d8+8) bludgeoning damage.

Frightful Presence

Each creature of the dragon's choice that is within 120ft 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.

Poison Breath (Recharge 5-6)

The dragon exhales poisonous gas in a 90ft cone. Each creature in that area must make a DC 22 Constitution saving throw, taking 77 (22d6) poison damage on a failed save, or half as much damage on a successful one.

Legendary Actions

The 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 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.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 15ft of the dragon must succeed on a DC 23 Dexterity saving throw or take 15 (2d6+8) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.