Nine Children of the Dragon (Mythic Trait; Recharges after a Short or Long Rest). If Arasta is reduced to 12 hit points, she regains 60 hit points, then she is enraged for one hour. While enraged, Xiao cannot Distinguish friend from foe, with the exception of members of the Zàng family.

Heishou Mutation [Chén]. At the start of Xiao's turn, if she has the stunned, paralyzed, petrified or poisoned condition, she may chose to end one of the aforementioned conditions on herself. If Xiao does not have one of the four mentioned conditions after this, everything within 15 feet of her gains 2D6 burn count

Fire Absorption. Whenever Xiao is subjected to Fire damage, she regains a number of Hit Points equal to the Fire damage dealt.

Firm as a Great Mountain. If Xiao would take 5 or less damage from an attack, that attacks damage becomes Zero. In addition, if Xiao is subject to a critical hit, She takes half damage from that attack.

Pú Láo. When Xiao starts her turn, Inflict 3D8 Burn to all hostile creatures within 30 feet of her. She can choose to have this also apply to objects.

Hugging Fire, Sitting on Brushwood. If Xiao is grappling a creature, the creatures burn count is multiplied by 1.5X instead of being halved as normal.

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

Force of a Wildfire. When Xiao deals fire damage, the creature that took damage also gains burn equal to half of the fire damage dealt(Rounded down). 

Tian Tian. If Xiao dies while her Nine Children of the Dragon trait is active, She cannot be revived by any spell lower than 7th level

Multiattack. Xiao makes two Guandao attacks, One of which may be replaced with a Tiěshānkào, Rush Down or Tāo Tiè attack.

Guandao. Melee Attack Roll: +11, reach 10 ft. Hit: 15 (2d8 + 6) Slashing damage plus 10 (3d6) Fire damage.

Tiěshānkào. Melee Attack Roll: +11, reach 5 ft. Hit: 11 (1D10 + 6) Bludgeoning damage plus 13 (3D8) Fire damage. Instead of inflicting burn via force of a wildfire, Xiao may chose to have the target take fire damage equal to their burn, then halve their burn count(rounded down)

Rush Down. Melee Attack Roll: +11, reach 5 ft. Hit: 19 (3d8 + 6) Piercing damage plus 6 (1d12) Fire damage. Before the attack roll is made, Xiao may move up to 30 feet to get as close as possible to the selected target, If 20 feet or more of movement were used, the attack deals an additional  6 (2d6) Fire damage

Tāo Tiè(Recharge 6). Xiao exhales fire in a 30-foot cone. Each creature in that area must make a DC 19 Dexterity saving throw, taking 31 (9d6) fire damage on a failed save, or half as much damage on a successful one. It ignites flammable objects in the area that aren't being worn or carried.

Forming Storm. Xiao can only use this bonus action if she has not made an attack. Until the end of her next turn, When Xiao next uses Tāo Tiè, Increase its Cones Size by 30 Feet, And Its fire damage is increased by 31 (9d6), to a total of 63 (18d6) Fire damage on a failed save, or half as much damage on a successful one.

Xiao can take 2 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. Xiao regains spent legendary actions at the start of her turn.

All-out War. Xiao makes one Guandao, Tiěshānkào, or Rush Down attack

Sturdy Defense. Xiao gains 4d10 Temporary hitpoints, If Xiao has these hitpoints at the start of her next turn, they are removed and she gains +2 bonus to ability checks, attack rolls and saving throws until she ends her turn.

Chī Wěn(Costs 2 Actions) Xiao makes two Guandao attacks, then gains burn count equal to the burn inflicted by the two attacks

If the Xiao's Nine Children of the Dragon trait has activated in the last hour, she can use the options below as legendary actions.

Violent Flame. Xiao makes one Tiěshānkào attack, then, if it hit, doubles the burn on all creature within 30 feet of the target

Emotional Turbulence(Costs 0 Actions). Xiao gains 3d10 burn count