Artaxarxes, the Ancient Red Wyrm Demigod

Artaxarxes, the Ancient Red Wyrm Demigod
Gargantuan Dragon, Chaotic Evil

Armor Class: 25 (natural armor)
Hit Points: 825 (50d20 + 350)
Speed: 40 ft., climb 40 ft., fly 120 ft.

STR: 34 (+12)
DEX: 14 (+2)
CON: 25 (+7)
INT: 26 (+8)
WIS: 22 (+6)
CHA: 30 (+10)

Saving Throws: Dex +9, Con +14, Wis +13, Cha +17
Skills: Perception +20, Stealth +9, Arcana +15, History +15, Intimidation +17
Damage Immunities: Fire
Condition Immunities: Charmed, Frightened
Senses: Blindsight 120 ft., Darkvision 240 ft., Passive Perception 30
Languages: Common, Draconic, Infernal, Abyssal, Celestial
Challenge Rating: 30

Traits:

Legendary Resistance (5/Day): If Artaxarxes fails a saving throw, he can choose to succeed instead.

Magic Resistance: Artaxarxes has advantage on saving throws against spells and other magical effects.

Demigod Powers: As a demigod, Artaxarxes has the following additional traits:

    Time Manipulation: Artaxarxes can manipulate the flow of time, allowing him to rewind, slow down, or speed up time in a limited area.
    Immortality: Artaxarxes does not age and cannot die of old age.

Spell-Like Abilities: Artaxarxes can innately cast the following spells, requiring no material components:

At-will: detect magic, mage hand, prestidigitation, minor illusion, suggestion
3/day each: counterspell, dispel magic, haste, slow, dimension door
1/day each: time stop, meteor swarm, power word kill, plane shift

Actions:

Multiattack: Artaxarxes can use his Frightful Presence. He then makes four attacks: one with his bite, two with his claws, and one with his tail.

Bite: Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 27 (4d10 + 12) piercing damage plus 18 (4d8) fire damage.

Claws: Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 23 (4d6 + 12) slashing damage.

Tail: Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 25 (4d8 + 12) bludgeoning damage.

Frightful Presence: Each creature of Artaxarxes' choice that is within 240 feet of him and aware of him must succeed on a DC 25 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 Artaxarxes' Frightful Presence for the next 24 hours.

Legendary Actions:

Artaxarxes 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. Artaxarxes regains spent legendary actions at the start of his turn.

    Detect: Artaxarxes makes a Wisdom (Perception) check.
    Tail Attack: Artaxarxes makes a tail attack.
    Wing Attack (Costs 2 Actions): Artaxarxes beats his wings.