Asyyal, The Abyssal Dragon

Magic Weapons. Asyyal's weapon attacks are magical.

Legendary Resistance:(15/day) If Asyyal Fails a saving throw, it can choose to succeed instead.

Frantic Behavior: When Asyyal hits 50% health, all of his attacks deal a additional +10 damage. When Asyyal hits 25% health, This effect increase by 5. If Asyyal's Demonic Deity Feature is activated, Asyyal maintains these buffs. When Asyyal reaches 1000 Hitpoints remaining for the second time, the effects increase by 15. When Asyyal reaches 500 hitpoints remaining for the second time, the effects increase by 10.

Chromashift: The Abyssal Dragon is able to control each of its scales Color, and how metallic it looks. It can use this ability to fool travelers from afar into thinking it is another type of dragon. By Succeeding a DC 25 Perception Check, A traveler discovers its true species.

Magic Resistance. The Abyssal Dragon has advantage on saving throws against spells and other magical effects.

Abyssal Scales. Any time the Abyssal Dragon is targeted by a Magic Missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 2 to 5, the Abyssal Dragon is unaffected. On a 6, the Abyssal Dragon is unaffected, and the effect is absorbed, and the Abyssal Dragon can use it as if it was casting it as a Spell by using its action.

Siege Monster. The Abyssal Dragon deals double damage to objects and structures.

Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).

In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

Demonic Deity: If Asyyal would drop to 0 Hit Points, he instead resets his current hitpoints to 2000, and gains access to his Mythic Actions(Same mechanics as Legendary actions). Upon being Defeated after this feature has been used, Award the party an additional 1000000 Exp. (1155,000 Exp total)

Immortal: If Asyyal's physical form would be destroyed, it will regenerate on his Plane within 5 minutes.

Multiattack: Asyyal makes 3 attacks, two with it's claws, and one with it's bite.

Greater Multiattack: Asyyal makes 5 attacks, two with it's Claws, 1 with its Bite, one with its Tail(Use either Whip or Tail Stab), and one with a breath weapon. (Recharge 10-12) Roll a d12 to regain this action.

Action Melee Attack. Claw: +29 to hit, reach 5 ft., 1 target. Hit: 103 (16d12 + 0) Slashing damage. 

Action Melee Attack. Bite: +29 to hit, reach 5 ft., 1 target. Hit: 108 (16d12 + 5) Piercing damage.  The target must make a DC 27 Constitution Save, or become poisoned, and take 4d6 poison damage at the start of its own turn. The target can repeat the save at the end of each turn, ending the effects on a success

Action Melee Attack. Whip: +29 to hit, reach 10 ft., 1 target. Hit: 137 (25d10 + 2) Slashing damage. The Target must make a DC 25 Dexterity saving throw, or be knocked prone. The target can use half its movement to stand back up.

Action melee attack. Tail Stab: +29 to hit, reach 10 ft,  1 target. Hit 664 (120d10 + 4) Piercing damage. 

Action melee attack. Clamp Down:  +29 to hit, Range 5 feet, 1 target. Hit: 330 (60d10 + 0) The Target is now grappled, and must make a DC 25 Dexterity saving throw to escape. If Asyyal uses a Bite, Clamp Down, or Breath weapon attack, or is damaged, The creature is no longer grappled, and falls Prone 5 feet in front of Asyyal.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 31 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Breath of the Demonic Deity (Recharge 20). Asyyal exhales godly energy in a 500 ft. cone. Every creature in the targeted area must make a DC 40 Dexterity saving throw, taking 2100 (200d20) damage on a failed save, or half as much damage on a successful one. This Damage cannot be resisted, ignored, or be a weakness.(Roll a d20 to regain this action)

Tighten the hold. The Abyssal Dragon can use its bonus action to close its jaws further, dealing 110 (20d10 + 0) Piercing Damage to any creature that is currently grappled due to its Clamp Down attack.

React:  When the Abyssal Dragon is attacked, the Abyssal Dragon may take a action to attack the last creature that attacked it.

Reactive: The dragon has a reaction for each turn of combat

The Abyssal Dragon is able to take A legendary action at the end of another creatures turn in combat, and regains spent actions at the start of its turn. It has 3 Legendary Actions

Bite. The Abyssal Dragon takes a bite action

Multiattack(2 Actions): The Abyssal Dragon takes a Multiattack Action

Recharge(2 Actions): Asyyal's Breath of the Demonic Deity attack is instantly recharged.

Rest: Asyyal gains all the benefits of a Short Rest, and regains all used actions.

Demolish: Asyyal selects up to 5 creatures. A creature can be selected up to 5 times. The Creature must make a DC 30 Constitution saving throw, or take 90 Force Damage. If a Creature is reduced to 100 hp by this Action, Power Word Kill is casted on them.

Cripple: Asyyal Selects up to 5 creatures. Each Creature must make a DC 30 Constitution saving Throw, or be Incapacitated, Blinded, Deafened, Gain 5 levels of Exhaustion, Frightened, Incapacitated, Paralyzed, Poisoned, Stunned, Restrained, and Knocked Prone.

Deity: Asyyal casts any 5 spells he wants. He suffers no drawbacks from casting spells such as Wish, and requires no material components. If a Spell requires concentration, a invincible spirit is summoned to maintain concentration on it.