Ancient Red Dragon

3/day. If the ancient red 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

Melee Weapon Attack: +17 to hit, reach 15 ft.. Hit: 21 (2d10 + 10) piercing plus 14 (4d6) fire damage.

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

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

Each creature of the ancient red dragon's choice that is within 120 ft. of the dragon and aware of it must succeed on a DC 21 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 red dragon's Frightful Presence for the next 24 hours.

Recharge 5–6. The ancient red dragon exhales fire in a 90-foot cone. Each creature in that area must make a DC 24 Dexterity saving throw, taking 91 (26d6) fire damage on a failed save, or half as much damage on a successful one.

Melee Weapon Attack: +17 to hit, reach 20 ft.. Hit: 19 (2d8 + 10) bludgeoning damage.

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

The ancient red dragon makes a tail attack.

Costs 2 legendary actions. The ancient red dragon beats its wings. Each creature within 15 ft. of the ancient red dragon must succeed on a DC 25 Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. The ancient red dragon can then fly up to half its flying speed.