Boris, Lord of House Redoran

Legendary Resistance (5/Day). If Boris fails a saving throw, he can choose to succeed instead. If he chooses to, he loses access to his burning presence until the start of his next turn.

Empowered Strikes. Boris' attacks are considered magical for the purpose of overcoming resistances and immunities.

Evasion. When subjected to an effect that allows Boris to make a dexterity save to take half damage, he instead takes no damage on a successful the saving throw, and only half damage on a failure. 

Shapechanger. Boris can use his action to polymorph into a gargantuan dragon, or back into his true form, which is a large humanoid. While in this form, he gains access to his mythic actions. Any equipment it is wearing or carrying isn't transformed. He reverts to his true form if he dies.

Multiattack. Boris can use his Burning Presence. Then make four Unarmed Attacks.

Unarmed Attacks. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit:  20 (2d10 + 10) [piercing] damage, plus 20 (4d10) [fire] damage.

Burning Presence. Each creature that is within 120 feet of Boris must make a DC 29 Constitution saving throw. On a failure, each creature in the area takes 422 (18d12+305) fire damage and become blinded. On a success the creature takes half as much damage and is not blinded. Boris can render his Burning Presence inactive (or reactivated it again) freely.

Revoke Fire Immunity (Recharge 5-6). Boris marks one creature or object he can see, the target loses any resistance or immunity against fire damage for the next hour. If Boris is hit, he'll need to make a concentration check equal to 6 + the damage dealt to maintain the mark. On a failure, the mark fizzles out and the target's resistance or immunity to fire is restored. Boris can mark a number of targets equal to his Charisma Bonus

Deflect Attack. In response to being hit by an attack, Boris deflects it. The damage he takes from the attack is reduced by 1d10+25. if the damage is reduced to 0, Boris catches it with a free hand. If the attack hit him by 5 or less, then he can make a ranged attack using the missile with a +18 to hit and a +10 to the damage.

Boris can take 4 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 its turn.

Unarmed Attack. Boris makes one additional unarmed attack.

Flashfire Fist: Jetburn (Cost 2 Actions). Boris concentrates his flames into a white-hot point on his fist and punches, sending a fiery beam into his target while knocking them back. Each creature within the area (90 foot long 5 foot wide line) must make a DC 25 Strength saving throw, taking 91 (26d6) fire damage and be pushed up to the end of the beam on a failed save. On a successful save, The creature instead suffers half the damage and isn't pushed.

Flashfire: Hellfire Strom (Costs 2 Actions). Boris creates a blazing whirlwind of roaring fire surrounding him, creatures up to 60 feet of him must roll a strength saving throw (DC 25) to stay in place or be moved 60 feet in one direction of his choice.

Flashfire: Ignited Arrow (Costs 2 Actions). Ranged Spell Attack: +17 to hit, range 150/600 ft., one target. Hit: 20 (4d10) fire damage. If Boris rolled a 20 on the attack roll, the arrow explodes up to a 20 ft. radius and all creatures caught in the area suffer an additional 8d6 fire damage.

Multiattack. While Boris is in his dragon form, he can use its Burning Presence. Boris can use his Burning Presence. He then makes four attacks: one with its bite and three with its claws (dragon form)

Bite. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) piercing damage plus 40 (4d10) fire damage.

Claw. Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: 17 (2d6 + 10) slashing damage plus 20 (4d10) fire damage

Tail. Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: 19 (2d8 + 10) bludgeoning damage plus 20 (4d10) fire damage.

Burning Presence. Each creature that is within 120 feet of Boris must make a DC 29 Constitution saving throw. On a failure, each creature in the area takes 422 (18d12+305) fire damage and become blinded. On a success the creature takes half as much damage and is not blinded. Boris can render his Burning Presence inactive (or reactivated it again) freely.