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

Multiattack.  Zamrunan can use his Frightful Presence.  He then makes three attacks: one with his bite and two with his claws.

Bite.  Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 18 (2d10 + 7) piercing damage plus 7 (2d6) fire damage.

Claw.  Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 7) slashing damage.

Tail.  Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 16 (2d8 + 7) bludgeoning damage.

Frightful Presence.  Each creature of Zamrunan's choice that is within 120 feet of him and aware of him must succeed on a DC 19 Wisdom saving throw or become frightened for one 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 Zamrunan's Frightful Presence for the next 24 hours.

Fire Breath (Recharge 5–6).  Zamrunan 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.

Zamrunan 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.  Zamrunan regains spent legendary actions at the start of his turn.

Detect.  Zamrunan makes a Wisdom (Perception) check.

Tail Attack.  Zamrunan makes a tail attack.

Wing Attack (Costs 2 Actions).  Zamrunan beats his wings.  Each creature within 10 feet of the dragon must succeed on a DC 21 Dexterity saving throw or take 14 (2d6 + 7) bludgeoning damage and be knocked prone.  Zamrunan can then fly up to half his flying speed.