Multiattack

The dragon uses its Frightful Presence. It then makes three attacks: one with its Bite and two with its Claws.

Bite

Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) piercing damage plus 14 (4d6) poison damage.

Claw

Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: 17 (2d6 + 10) slashing damage.

Tail

Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: 19 (2d8 + 10) bludgeoning damage.

Frightful Presence

Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 20 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 a cone of black, poisonous gas in a 90-foot cone. Each target in that area must make a DC 25 Constitution saving throw. On a failure, a creature takes 91 (26d6) poison damage and is poisoned until cured by the greater restoration spell or similar magic. On a success, a creature takes half the damage and isn't poisoned.