Archon the Eldest of Tharizdun. The first of the Elder Evils.

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

Special Equipment. Claws of decay decay + 12 to hit reach 15 feet, Decay hit 28 (2d12+7 slashing) (2d8 necrotic+6)+ (2d10+ 6)acid

The Many. If one Archon is slain, another will seek out the last place he fell 1d100 all Archons know who killed one of them.

Unusual Nature. Archon doesn’t require air, food, drink, or sleep.

333 eyes, Any target that stands within 60 feet of Archon at the start of their turn must make either an athletics or a acrobatics check DC 21 or be grappled at the start of their turn.

Multiattack. Archon uses Flight of the Damned (if available), will of Tharizdun, or Spellcasting. He then makes two attacks with Claws of Decay

Claws of Decay. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 7 (2d12+ 7) slashing damage plus 9 (2d8+6) necrotic damage. If the target is a creature, it is afflicted by entropic magic, taking 9 (2d8) necrotic damage at the start of each of its turns. Immediately after taking this damage on its turn, the target can make a DC 20 Constitution saving throw, ending the effect on itself on a success. Until it succeeds on this save, the afflicted target can't regain hit points and loses 1 AC.

Flight of the Damned (Recharge 5–6). Archon conjures a torrent of twisting void , a wall of thick shadow like fire that fill a 120-foot cone and pass through all creatures in that area before dissipating. Each creature in that area must make a DC 22 Constitution saving throw. On a failed save, the creature takes 36 (8d8) necrotic damage and is frightened of Archon for 1 minute. On a successful save, the creature takes half as much damage and isn’t frightened. A frightened creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

The will of Tharizdun. Archon calls the will of Tharizdun to consume the thoughts of one creature he can see within 120 feet of himself. The target must make a DC 22 Constitution saving throw, taking 96 (8d8 + 60) phyic damage on a failed save, or half as much damage on a successful one. A Humanoid killed by this magic is consumed and becomes nothing but an extention of Tharizdun and claws of decay will now deal an extra attack each round.

 Discord and Woe (2/Day). One creature within 100 miles of the essence that the essence is aware of must make a DC 24 Wisdom saving throw. A creature automatically succeeds if it is immune to being charmed. On a failed save, the target must target its allies with attacks and other damaging effects for 1 minute. The target 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 Archon's Discord and Woe for the next 24 hours.

Vile Teleport. Archon teleports, along with any equipment he is wearing or carrying, up to 30 feet to an unoccupied space he can see. He can cause each creature of his choice within 15 feet of his destination space to take 10 (3d6) psychic damage. If at least one creature takes this damage, Archon regains 80 hit points.

Archon can take up to three reactions per round but only one per turn.

Dread Counterspell. Archon utters a prayer to Tharizdun to interrupt a creature that Archon can see that is casting a spell. If the spell is 4th level or lower, it fails and has no effect. If the spell is 5th level or higher, Archon makes an wisdom check (DC 10 + the spell’s level). On a success, the spell fails and has no effect. Whatever the spell’s level, the caster takes 10 (3d6) psychic damage if the spell fails.

Fell Rebuke. In response to being hit by an attack, Archon's flesh twists the pain and deals it back, dealing 10 (3d6) choice of lightning, thunder, cold or fire damage to the attacker, and Archon teleports, along with any equipment he is wearing or carrying, up to 30 feet to an unoccupied space he can see.

(Mythic only) Time corruption.  Tharizdun can command fate it's self within this realm. Once per round as a reaction a hostile creature of the Archon's choice will be effected by Time corruption and must make a DC charisma saving throw of 20 if they fail they must re-roll an action or a check and take the lower of the two.

 This form is only available in the centre of Archon's lair. It can be accessed if he has been successfully banished, polymorphed or slain.

Tharizdun itself is now before you the size of archon is now replaced with gargantuan form.

It's form is absolute, unless its will is unmoved its form cannot change, it cannot be banished.

• Damage Resistances cold, fire, lightning and magic, phycic
• Damage Immunities acid, poison; bludgeoning, piercing, and slashing from nonmagical attacks, necrotic 
• Condition Immunities charmed, deafened, exhaustion, frightened, petrified, poisoned, unconscious.
• Condition Vunrebility radiant, force.
• Senses truesight 120 ft., blindsight 500 ft., passive Perception 25
• Languages understands all languages, telepathy 1,000 ft.

Multiattack. The Archon makes four attacks: two tentacle and two with its bite. It then uses Corporeal Instability.

Tentacle. Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: 28 (4d8 + 10) bludgeoning damage plus 7 (2d6+10) necrotic damage, and the target is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the target takes 10 (3d6+10) necrotic damage at the start of each of its turns. The Target is unable to heal while grappled.

Bite. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 36 (4d10 + 14) piercing damage plus 7 (4d6+10) acid, cold, fire, lightning, or thunder damage (Arxhon's choice). When Bite has made a successful hit the target must make a successful Dex saving throw of 20 or be consumed by the Avatar form. Consumed targets take (2d10) acid+(3d6+10) force damage lose 2 AC at the start of each turn until the target reaches 0 HP, all AC is removed or the target makes a successful Str/Wis/Cha/Con saving throw of 22. If the target has lost all AC they take an additional (1d12+10) of psychic damage.

The Epoch of Oblivion may now be used as a bonus Action 

Corporeal Instability. Archon targets one creature it can see within 60 feet of it. The target must succeed on a DC 24 Constitution saving throw or take 22 (4d6 + 10) necrotic damage + (2d10+6) lightning damage and become corrupted for 1 minute.
A corrupted creature's flesh constantly melts, flows, writhes, and boils. The creature has disadvantage on attack rolls, its speed is reduced by half, and whenever it takes damage, its hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The creature dies if its hit point maximum is reduced to 0.
The corrupted creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

 Vile tellaport is no longer an option.

Tharizduns attempt to break the wills of the PCs is now at the start of each round the Avatar is being engaged in combat. (Lair only)

Fell Rebuck is no longer an option 

Has access to time corruption.