Phenax, the Ascended

Ascension (Mythic Trait). If Phenax is reduced to 0 hit points, he doesn't die or fall unconscious. Instead, he regains 250 hit points, additionally, he adapts the lessons he has learned into full abilities. He gains access to his Mythical Power.

Legendary Resistance (4/day). If Phenax fails a saving throw, he can choose to succeed instead.

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

Special Equipment. Phenax carries the shortsword named Deception's Edge and the longsword named Truth's Sting. In the hands of anyone other than Phenax, they are mundane weapons unless Phenax allows them to be otherwise.

Divine Nature. Phenax doesn't require air, food, drink, or sleep.

Multiattack. Phenax uses Heart of Nyx (if available), Story's End, or Spellcasting. He then makes two attacks with Deception's Edge and/or Truth's Sting.

Heart of Nyx (Recharge 4-6). Phenax unleashes the raw power of the Heart of Nyx willing the battlefield to change and morph to his advantage. Phenax chooses any number of creatures within 120 feet of himself, pulling them along with himself to a different plane. Each creature chosen this way must make a DC 23 Dexterity saving throw, taking (6d10) force damage on a failed save, or half as much damage on a successful one. Phenax may reposition any creature who failed this saving throw to anywhere within 120 feet of himself and those creatures can not use reactions until the start of their next turn.

Story's End. Phenax bends reality to his will, attempting to end the very existence of one creature he can see within 120 feet of himself. The target must make a DC 23 Wisdom saving throw, taking (1d100 + 10) force damage on a failed save and half as much on a successful one. A creature killed by this power will cease to exist at the start of Phenax's next turn. This effect can only be undone by the Heart of Nyx.

Deception's Edge. Melee Weapon Attack: +16 to hit, reach 5 ft., 1 target. Hit: 10 (1d6 + 7) slashing damage and 9 (3d6) acid damage.                                                       Deception's Thrall: When Phenax hits a creature that has an intelligence score of 4 or higher with an attack using this sword, the target takes an extra 3d6 acid damage and must succeed on a DC 17 Charisma saving throw or be charmed by Phenax for 1 hour. If  Phenax attacks the creature again while it is charmed in this way, the extra acid damage increases to 10d6 and  the charmed condition ends. If the target succeeds on its saving throw or the charm ends for it, it can't be charmed again in this way for 24 hours.

Truth's Sting. Melee Weapon Attack: +16 to hit, range 5/15 ft., 1 target. Hit: # (1d8 + 7) slashing damage and an additional 3d6 radiant damage.                                             Binding Truth: When a creature is hit with this weapon, they become grappled as the bladed whip entangles them. Phenax may expend an attack to move the grappled creature anywhere within a 15 foot radius of himself. If a creature is moved this way, they must succeed a DC 17 Wisdom saving throw or take (6d6) radiant damage as the blade scorches every lie they've ever spoken on to their body.

Spellcasting. Phenax, the Ascended is a 20th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 23, +16 to hit with spell attacks). Phenax, the Ascended has the following Sorcerer spells prepared:

At will: Minor Illusion, Charm Person, Disguise Self, Silent Image, Silvery Barbs, Crown of Madness, Mirror Image, Suggestion, Fear, Major Image, Confusion, Greater Invisibility

2/day each: Hold Monster, Synaptic Static, Circle of Death, Dominate Monster

1/day each: Eyebite, Mental Prison, Power Word Pain, Power Word Kill, Power Word Stun, Power Word Kill

Empty Shadow. As a bonus action, Phenax melds into the shadows and teleports up to 40 feet in to another unoccupied spot that is dimly lit or dark. 

Divine Deception. When Phenax is attacked or would be effected by a spell or other magical ability, he can force a creature he can see within 120 feet of him to make a DC 23 Constitution saving throw, trading places with the target on a failed save.

Phenax can take 4 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. Phenax regains spent legendary actions at the start of his turn.

Truth or Lies (Costs 1 Actions). Phenax makes one melee weapon attack using Deception's Edge or Truth's Sting.

Quick Thinking (Costs 2 Actions). Phenax casts a spell that is available to him.

Rewrite the Story (Costs 3 Actions). Phenax changes the narrative of recent events that have transpired, allowing him to potentially escape danger. If Phenax was attacked or affected by a spell or ability the previous turn, instead apply the same attacks, spells, or effects to the creature who's turn it just was. reroll all attacks, ability checks, and saving throws, but reverse the roles of Phenax and the affected creature. If the affected creature takes no damage and is not effected by any spell or ability, the previous turn is unchanged, otherwise Phenax is instead unaffected and the creature takes the new effects. 

If Phenax's mythic trait is active, he gains each of the following abilities at the start of each of his turns one at a time until all are active.

Lessons of the Stranger King. Phenax's form shifts and dances chaotically in a madness inducing flurry of incomprehensible patterns. Phenax is under the effects of the Blur spell. In addition, if a creature deals damage to Phenax, they must make a DC 23 Wisdom saving throw or become effected by Crown of Madness. If a creature succeeds the saving throw, they are immune to this effect for 24 hours.

Lessons of the Nightmare Weaver. Phenax's form bends and twists, taking on the worst aspects of himself, shaping into the worst nightmares of all who look upon him. At the start of each creature's turn, if they can see Phenax, they must succeed DC 23 Wisdom saving throw or become frightened of Phenax until the end of their next turn. If a creature succeeds this saving throw two times, they become immune to the effect for 24 hours.

Lessons of the Star Walker. Phenax's mind reaches beyond the stars, beyond anything mortal or divine beings should ever see. His understanding of the cosmos has granted him power to better manipulate it. When a creature makes a saving throw to resist one of Phenax's spells, if that spell is from the school of Enchantment or Illusion, that creature has disadvantage on their saving throw.

Lessons of the Perfect Machine. Phenax becomes immune to the stunned and paralyzed conditions and other creatures attempting to cast a spell of 3rd level or lower must succeed a DC 23 Intelligence saving throw or fail to cast the spell.

Lessons of the Writhing Flesh. When Phenax is dealt damage, he gains resistance to whatever damage types were used against him after the damage is dealt. This ability resets at the start of his next turn.

Lessons of Ascension. The Heart of Nyx is nearly fully bonded to Phenax, the sheer power radiating from him is approaching unstoppable. In one more round, Phenax will become immune to all damage except damage dealt with the artifact known as The Key of Nyx.