Hinfeynzii

Breath Control. Hinfeynzii has exceptional control over his ability to breathe searing plasma. The Plasma Breath and Plasma Spear actions both use the dragon's shored up plasma reserve, so if one ability is used, it must recharge before the other can be used.

Legendary Resistance (5/Day). If Hinfeynzii fails a saving throw, he can choose to succeed instead.

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

Bite. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 13 (1d10 + 8) piercing damage plus 5 (1d10) fire damage.

Claw. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 22 (2d8 + 8) slashing damage.

Tail. Melee Weapon Attack: +17 to hit, reach 20 ft., one target Hit: 19 (2d10+8) bludgeoning damage.

Frightful Presence. 
Each creature of the dragon's choice that is within 120 ft. of the dragon and aware of it must succeed on a DC 22 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.

Plasma Breath (Recharge 5-6).
The dragon exhales crackling energy in a 90-foot cone, or a 180-foot line. Each creature in that area must make a DC 25 Dexterity saving throw, taking 98 (28d6) fire damage on a failed save, or half as much damage on a successful one. Fire damage dealt by the dragon’s breath bypasses fire resistance, but not immunity. All creatures within 60 feet of the dragon that can see it must succeed on a DC 25 Constitution saving throw or be blinded for 1d4 rounds.

Plasma Spear (Recharge 5-6).
Ranged Weapon Attack: +17, Range 600/1200 ft., one target Hit: 49 (14d6) fire damage plus 49 (14d6) lightning damage.
Fire damage dealt by the dragon’s breath bypasses fire resistance, but not immunity. This attack ignores any cover bonus to AC benefiting the target except for cover bonuses granted by objects made of adamantine. The target must succeed on a DC 25 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken. This reduction is permanent unless undone with magic such as with the Greater Restoration or Wish spells. On a critical hit, this attack severs one of the target’s limbs, if it has any.