Legendary Resistance (3/Day). If Ashtyrranthor fails a saving throw, it can choose to succeed instead.

Innate Spellcasting. Ashtyrranthor's spellcasting ability is Charisma. She can innately cast the following spells, requiring no material components:

1/day each: alarm, detect magic, gaseous form, misty step, passwall, see invisibility

Multiattack. Ashtyrranthor can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit:19 (2d10 + 8) piercing damage plus 7 (2d6) fire damage.

Claw. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit:15 (2d6 + 8) slashing damage.

Tail. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit:17 (2d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of Ashtyrranthor's choice that is within 120 feet 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.

Fire Breath (Recharge 5–6). Ashtyrranthor exhales fire in a 60-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 63 (18d6) fire damage on a failed save, or half as much damage on a successful one.

Detect. Ashtyrranthor makes a Wisdom (Perception) check.

Tail Attack. Ashtyrranthor makes a tail attack.

Wing Attack (Costs 2 Actions). Ashtyrranthor beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 22 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.