Heaven's Brilliance (Recharges after a Short or Long Rest). If the he would be reduced to 0 hit points, his current hit point total instead resets to 500 hit points, he recharges his Breath Weapon, and he regains any expended uses of Legendary Resistance. Additionally, the aspect can now use the options in the “Mythic Actions” section for 1 hour. Award a party an additional 155,000 XP (310,000 XP total) for defeating the Jade Emperor after his Heaven's Brilliance activates.

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

Divine Blade. When Yu-Huang hits with these weapons, they deal an extra 5d8 radiant damage (included in the attack).

Spellcasting. Yu-Huang can cast any spell

Multiattack "Dragon". Yu-Huang makes one Bite attack, one Claw attack, and one Tail attack. Bite, Claw and Tail attack is only available in his Dragon form.

Multiattack "Humanoid "  Yu-Huang makes three attacks with his Divine Blade.

Bite. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 23 (2d12 + 10) piercing damage plus 22 (4d10) force damage.

Claw. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 20) and is restrained until this grapple ends. Yu-huang can have only one creature grappled this way at a time.

Tail. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 23 (2d12 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 27 Strength saving throw or be knocked prone.

Divine Blade. Melee Weapon Attack:  +19 to hit, reach 5 ft., one target. Hit: 21 (2d10 + 10) slashing damage. 5d8 radiant damage

Breath Weapon (Recharge 5–6). Yu-huang uses one of the following breath weapons:

Exalting Breath. Yu-huang exhales the restoring winds of Heaven in a 300-foot cone. Each creature in that area of the aspect’s choice regains 71 (13d10) hit points, and each creature in that area of Yu-huang's choice that has been dead for no longer than 1 hour is restored to life with all its hit points.

Radiant Breath. Yu-huang exhales radiant flames in a 300-foot cone. Each creature in that area must make a DC 26 Dexterity saving throw, taking 66 (12d10) radiant damage on a failed save, or half as much damage on a successful one.

Change Shape. The Jade Emperor can magically transforms into any Humanoid or Dragon, while retaining his game statistics (other than his size). This transformation ends if the Jade Emperor is reduced to 0 hit points or if he uses a bonus action to end it.

The Jade Emperor 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 Jade Emperor regains spent legendary actions at the start of his turn.

Attack. The Jade Emperor makes one Claw or Tail attack. If in Human for he can make one attack with Divine Blade or a spell of 4th level or lower.

Furious Bite (Costs 2 Actions). The Jade Emperor makes one Bite attack. If the attack hits a creature, the target must succeed on a DC 27 Wisdom saving throw or become frightened of the Jade Emperor until the end of the target’s next turn.

If Yu-huang's Heaven's Brilliance trait has activated in the last hour, he can use the options below as legendary actions.

Heaven's Ward (Costs 2 Actions). Yu-Huang creates the light of Heaven around himself that protect him; he gains 84 temporary hit points until the start of his next turn.

Heaven's Light (Costs 3 Actions). Yu-huang conjures four enormous dragons of magical force that plummet to the ground at four different points he can see within 150 feet of him and then disappear. Each creature in a 20-foot-radius, 100-foot-high cylinder centered on each point must succeed on a DC 27 Dexterity saving throw or take 24 (7d6) force damage. A creature in the area of more than one dragon is affected only once.