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

Multiattack. Zagasar 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 15 ft., one target. Hit: 19 (2d10 + 8) piercing damage.

Blighted Claws. Melee Weapon Attack: +15 to hit,  reach 15 ft., one target. Hit: 19 (2d10 + 8) piercing damage. The Target must make a dc 19 Constitution saving throw, or be poisoned by 4d12 Blight Damage. the Target then has a lasting illness of Blight unless cured by a Cleric.

Tail. Melee Weapon Attack: +14 to hit, reach 20 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of Zagasar's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 18 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 Zagasar's Frightful Presence for the next 24 hours.

Breath Weapons (Recharge 5–6). The dragon uses one of the following breath weapons:

Fire Breath. Zagasar exhales fire in an 90-foot line that is 10 feet wide. Each creature in that line must make a DC 21 Dexterity saving throw, taking 56 (16d6) fire damage on a failed save, or half as much damage on a successful one.

Breath of the Blightful. Zagasar exhales an Acidic cloud in a 90-foot cone. Each creature in that area must succeed on a DC 21 Constitution saving throw or be burned and poisoned for 15 minutes. This effect ends for a creature if the creature dies or is healed with an antidote potion or by a cleric

Change Shape. Zagasar magically polymorphs into a humanoid or beast that has a challenge rating no higher than his own, or back into his true form. he reverts to his true form if he dies. Any equipment he is wearing or carrying is absorbed or borne by the new form (Zagasar's choice).

In a new form, Zagasar retains his alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. his statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

Zagasr 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. The dragon regains spent legendary actions at the start of his turn.

Detect. Zagasar makes a Wisdom (Perception) check.

Tail Attack. Zagasar makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats his wings. Each creature within 15 feet of Zagasar 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.