Ancient Green Dragon

The ancient green dragon can breathe air and water.

3/day. If the ancient green dragon fails a saving throw, it can choose to succeed instead.

3 legendary actions; one at a time at the end of another creature’s turn, regaining spent uses at the start of its turn

The ancient green dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Melee Weapon Attack: +15 to hit, reach 15 ft.. Hit: 19 (2d10 + 8) piercing plus 10 (3d6) poison damage.

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

Each creature of the ancient green dragon's choice that is within 120 ft. 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 ancient green dragon's Frightful Presence for the next 24 hours.

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

Recharge 5–6. The ancient green dragon exhales poisonous gas in a 90-foot 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.

The ancient green dragon makes a Wisdom (Perception) check.

The ancient green dragon makes a tail attack.

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