Aspect of Sardior

Crystal Wake (Recharges after a Short or Long rest). If the aspect would be reduced to 0 hit points, his current hit point total instead resets to 500 hit points, he recharges his breath weapon, and 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 aspect of Sardior after his Crystal wake activates.

Legendary Resistance (5/Day). If the aspect fails a saving throw, it may choose to succeed instead.

Multiattack. The aspect makes one Bite attack, one Claw attack, and one Tail attack.

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. The aspect 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.

Psionic Breath (Recharge 5-6). The aspect exhales a 300-foot cone of gravitational force. Each creature in the area must make a DC 26 Dexterity saving throw, taking 64 (12d10) force damage on a failed save, or half as much on  successful one.

Change shape. The aspect magically transforms into any humanoid or beast creature, while retaining all his game statistics (other than his size). This transformation ends if the aspect is reduced to 0 hit points or if he uses a bonus action to end it.

Psychic step. The aspect magically teleports to an unoccupied space it can see within 100 feet of it.

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

Attack. The aspect makes on bite or claw attack.

Furious bite (Costs 2 Actions). The aspect 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 aspect until the end of the target's next turn.

If the aspect's Crystal Wake trait was activated in the last hour, he can use the options below as legendary actions.

Crystal shatter (Costs 2 Actions). The aspect is surrounded by a 250 foot sphere made of pure gemstones, giving him 77 temporary hit points until the start of the next turn. If any creatures attempt to attack the Aspect while the temporary hit points are not at 0, they take 1 D12 Force damage.

Gemstone Syphon (Costs 3 Actions). The aspect absorbs all gem dragon's psionic powers and gains 100 temporary hit points until the end of the turn. He also summons a 100 foot cylinder of psionic energy, anything inside becomes incapacitated.