Ancient Infinite Multi-Dimensional Aberrant Dracolich (Ultra-Elemental)

Higher CR: This creature has a CR of 55, not 30, and upon defeat this will reward 1,620,000 xp.

Radiation: This creature is immune to radiation. When another creature hits this with a melee attack, they take 4d12 + 2 radiation damage.

Undying Dracolich: While this creatures phylactery is intact, when this creature reaches 0 HP, it becomes unconscious, and this creature's heart opens up and is available to attack. It's heart has 1000 hp, and this creature's heart heals for 10d20 after a long rest. 1 minute later this rolls 50d20. This creature resurrects and it's HP becomes that number that it rolled.

Phylactery: This creature has a phylactery. This creature cannot die until it's phylactery is destroyed. Every time this creature kills 50 creatures without becoming unconscious , it can create a new phylactery, in addition to all existing phylacteries. When all phylacteries are destroyed, this creature will immediately crumble to ashes and die. The phylactery is stored in an object of this creature's choice. When spawned this creature's first phylactery is stored inside it's heart. When one of this creature's phylacteries are destroyed, this takes 2d6 + 1 damage and knows of the phylactery's destruction.

Undyinger Dracolich: (Once per week): When every one this this creature’s phylacteries are destroyed, it can choose to create another one from an object within 50 ft. of it. This prevents the creature from dying.

Chaotic Storm: While this creature is alive, it can use a bonus action to create or destroy an Aberrant elemental storm 50 - 1000 ft. around it, decreasing view radius by 20 ft. for all creatures besides this one caught in the storm. Also all creatures in the storm take 8d8 radiation damage at the start of each of their turns. If a creature dies from radiation in this way, instead of dying, the creature becomes under the control of this Ancient Aberrant Dracolich, and is now immune to radiation.

Absorbent Bones: If a spell is cast at this creature that requires an attack roll, this creature heals instead of taking damage.

Nope: If this creature takes more than 500 damage in a single attack, the damage is reduced by 20d20, and the attacker takes that much damage.

Yep: if this creature takes less than 10 damage in a single attack, the attacker takes 20d20 damage and this creature heals for 12d20 health.

Curse: When a creature is hit by an attack from this creature, they become cursed. They become plagued by nightmares, and gain no benefit from short or long rests. When they attempt to take a long rest, they must succeed on a DC 23 Con saving throw or take 6d8  necrotic damage. This curse lasts for 1d8 + 2 days.

Terrifying Presence: If a creature is within line of sight and less than 100ft. away from this creature, at the start of their turn they must make a DC 25 Wisdom saving throw. On a fail, they are frightened for 10 minutes. A creature can roll a DC 23 Wisdom saving throw to become unfrightened at the end of each of their turns. Once a creature succeeds on a frightened check, they are immune to being frightened by this creature for 24 hours.

Spellcasting: The Ancient Aberrant Dracolich is a level 30 spellcaster. This creature has a spell save DC of 29, and a spell attack modifier of +19. The Ancient Aberrant Dracolich has the following spells prepared:

• Cantrips (as a reaction or bonus action): Acid splash, and Emit radiation. 
• 2nd Level (as a bonus action or reaction): Darkness, Hold person,
• 3rd level (as a bonus action or reaction): Animate dead(permanent until they die), Bestow curse, fear, fireball, lightning bolt, vampiric touch.
• 4th level (as a bonus action or reaction): Black tentacles, blight.
• 6th level (at will): Create undead. (permanently under this creature's control, until they die)
• 7th level (1 spell slot): Finger of death.
• 8th level (1 spell slot): Dominate monster (on a success, the creature becomes an aberrant version of itself, and is permanently under this creatures control.)
• 9th level (once per day): Wish, Meteor Storm

Multi-attack: This creature makes five attacks: Two claw attacks, one bite attack (if possible), one tail attack, and one breath attack.

Dragon breath: Breath weapon attack: As an action, this uses a dragon breath attack. It can be the breath attack of any dragon, and as well as the normal damage type, the damage type is also radiation and does an additional 4d8 radiation damage.

Corrupting breath: Breath weapon attack:  This casts the corrupt spell in a 90 ft. cone. All creatures with 10 constitution or less immediately fail the saving throw.

Tail attack: Melee Attack: +19 to hit, reach 25 ft., all targets within 10 ft. in one direction. Hit:  6d20 bludgeoning damage. 

Claw: Melee Attack: +19 to hit, range 15 ft., 1 target. Hit: 12d20 slashing damage.

Bite: Melee Attack: +24 to hit, range 10ft., 1 target. Hit: 15d20, and the target is now grappled (Escape Dc 24). This creature cannot use the bite attack if a creature is already grappled.

Skeletal war: (three times a short rest): This summons 1d20 + 2 skeletons to aid this in battle. These go directly after this in initiative. This creature can use a bonus action to dispel these skeletons.

Skeleton Dragons: This summons 1d10 + 2  dracoliches. These go directly after this in initiative. This creature can use a bonus action to dispel them. While these dracoliches are alive, this creature and it's phylacteries cannot be destroyed or damaged.

Polymorph: This creature magically transforms into another creature of this creature’s challenge rating or lower. It can choose a creature of any size. While transformed , this creature keeps all of its abilities and attacks, except for its melee attacks and breath attacks. This creature can use a bonus action to transform back. If this creature dies while polymorphed, it reverts back into it’s normal form.

 Planar Shift: This creature moves to another plane of existence.

Teleport: This creature moves to an unoccupied location within its line of sight and less than 1000ft. away.

Reaction Attack: This makes a melee attack.

Reacting summoning: If this is at 1/2 of it's hp or less, it can summon 1d4 - 1 dracolitches.

The Ancient Aberrant Dracolich can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only during another creature’s turn. The dragon regains spent legendary actions at the start of its turn.

Legendary Resistance: (10 times a short rest): If this fails a saving throw, it can choose to succeed instead.

Dragon's control: Any dragons within 100 ft. of this are now controlled by this creature.

Melee Attack: This creature makes a melee attack.