Platinum Brilliance (Recharges after a Short or Long Rest). If the aspect would be reduced to 0 hit points, its current hit point total instead resets to 492 (80% of it's maximum hit points) hit points, it recharges its Breath Weapon, and it regains any expended uses of Legendary Resistance. Additionally, the aspect , can now use the options in the "Mythic Actions" section for 1 hour. Unusual Nature. The Aspect of Tiamat doesn't require food or drink. Legendary Resistance (5/Day). If the dragon fails a saving throw, it can choose to succeed instead.
Multiattack. The aspect can use its Frightful Presence. It then makes three attacks: one with its bite, one with its claws, and one tail attack Bite. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: (2d12 + 10) piercing damage plus (4d10) force damage. If the attack hits a creature, the target must make a DC 27 (8 + Prof + Cha) Wisdom saving throw or become frightened of teh aspect until the end of its next turn. Claw. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: (2d10 + 10) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 29 (10+Athletics)) and is restrained until this grapple ends. The aspect can only have one creature grappled this way at a time. Tail. Melee Weapon Attack: +19 to hit, reach 25 ft., one target. Hit: (2d12 + 10) bludgeoning damage. If the target is a creature, it must make a DC 27 (8 +Prof + Str) Strength saving throw or be knocked prone Breath Weapon (Recharge 5-6). The aspect uses one of the following breathe weapons. Platinum Breathe. The aspect exhales platinum flames in a 300-foot cone. Each creature in that area must make a DC 27 (8 + Prof + Str) Dexterity saving throw, taking 104 (19d10) radiant damage on a failed save, or half as much damage on a successful one. Exalting Breathe. The aspect exhales restorative winds in a 300-foot cone. Each creature of the aspects choice regains 71 (13d10) hit points, and each creature of the aspect's choice that has been dead for no longer 1 minute is restored to life with all it's hit points.
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 their turn. Detect. The dragon makes a Wisdom (Perception) check. Attack. The dragon makes a claw or tail attack. Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 30 ft. of the dragon must succeed on a DC 27 (8 + Prof + Str) Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.