Hastur, the King in Yellow

Large mythic aberration (Great Old One), unaligned

Armor Class 30 (yellow robes)
Hit Points 3,503 (226d10 + 2,260)
Speed 30 ft., fly 120 ft. (hover)

STR	DEX	CON	INT	WIS	CHA
18 (+4)	20 (+5)	30 (+10)	26 (+8)	19 (+4)	36 (+13)

Saving Throws Str +16, Dex +17, Con +22, Int +20, Wis +16, Cha +25
Skills Arcana +32, Deception +37, Insight +28, Perception +16, Religion +32
Damage Resistances acid, cold
Damage Immunities psychic; damage from non-Epic creatures
Condition Immunities blinded, charmed, exhaustion, frightened, stunned, unconscious
Senses blindsight 120 ft., passive Perception 26
Languages telepathy, unlimited range to any creature on the same plane
Challenge Mythic 10

SPECIAL TRAITS

• Great Old One Magic. Hastur does not require material components for spells, may speak a spell’s verbal components telepathically, and does not need to concentrate on spells to maintain their effects for the duration.
• Infectious Madness. Hastur’s spells and abilities induce madness. Each time a creature fails a death, Intelligence, Wisdom, or Charisma saving throw against Hastur, the creature gains one level of yellow mania. Mythic Resistance. If Hastur fails a saving throw, it may expend the use of an unspent legendary action to succeed instead.
• Out of Touch. Hastur barely registers reality as we know it. If Hastur takes 30 or less damage from a single instance of damage it instead takes no damage.
• Spellcasting. Hastur is a 30th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 33, +25 to hit with spell attacks). When Hastur would deal damage with a spell or magical effect, it may choose to instead deal psychic damage. Hastur can innately cast the following spells:
  • At will (cast as an 8th-level spell): harm, hideous laughter, mass suggestion, phantasmal force, synaptic static*
  • 9/day: feeblemind, globe of invulnerability, planeshift, psychic scream†, teleport

Hastur has the following Epic spells prepared:

• Tier 1 (7 slots): antimagic ray, dimensional mastery, hideous mandate, infinity room, magic bullet, night terror
• Tier 2 (6 slots): determinism, enslave, implosion, kinetic control
• Tier 3 (5 slots): soul harvest, sphere of ultimate destruction
• Unearthly Grace. Hastur moves with an otherworldly air, granting him the following benefits:
  • Hastur may take both a Dash and Disengage action as a single bonus action.
  • Once on each of its turns, if Hastur is prevented from taking an action (including bonus, legendary, and mythic actions) as the result of a condition or magical effect, it may spend half its movement (minimum of 5 ft.) to become immune to that condition or magical effect until the end of that turn.

MYTHIC ACTIONS

On initiative count 20 (losing initiative ties), Hastur takes a mythic action to cause one of the following effects. Hastur can cause the same effect multiple times in a row.

• Active Hallucinations. Hastur magically teleports to a space it can see within 80 feet of it. Additionally, six illusory copies of Hastur are created in unoccupied spaces it can see within 80 feet of it. The illusions function as Hastur does and act on its turn, but their actions cannot harm or affect anything. If damaged, the illusions are destroyed, but otherwise are indistinguishable from Hastur. If they are not destroyed, the illusions disappear on the next initiative count of 20.
• Present the Yellow Sign. Hastur presents the Yellow Sign, an eldritch glyph that heralds its profane power. All creatures within 60 feet of it that can see Hastur must succeed on a DC 33 Wisdom saving throw or gain three levels of yellow mania, or one level on a success. Unless surprised, a creature can use its reaction to avert its eyes to automatically succeed on the saving throw. A creature that averts its eyes in this manner cannot target Hastur until the end of its next turn.

ACTIONS

• Multiattack. Hastur makes three Tattered Lash attacks or casts two non-Epic spells.
• Overwhelming Presence (Recharge 5–6). Hastur asserts total authority over the minds of creatures around it. Until the start of Hastur’s next turn, the first time a creature attempts a saving throw against Hastur, it cannot succeed on that saving throw.
• Revel in Madness (Recharge 5–6). Hastur shatters the minds of its enemies. Each creature with one or more levels of yellow mania in a 1-mile radius centered on Hastur must succeed on a DC 33 Intelligence saving throw or take 55 (10d10) psychic damage per level of yellow mania it has. A successful saving throw halves the damage.
• Tattered Lash. Melee Weapon Attack: +17 to hit, reach 50 ft., one target. Hit: 38 (6d10 + 5) slashing damage and the creature is pushed up to 50 feet away from Hastur.

LEGENDARY ACTIONS

Hastur can take 4 legendary actions, choosing from the options below. Only one legendary action can be used at a time, and only at the end of another creature’s turn. Hastur regains spent legendary actions at the start of its turn.

• Cast a Spell. Hastur casts a non-Epic spell.
• Cast an Epic Spell (Costs 2 Actions). Hastur casts an Epic spell.
• Dark Impulse. Hastur chooses a creature it is aware of with one or more levels of yellow mania and forces it to attempt a DC 33 Wisdom saving throw. On a failure, the creature immediately uses its reaction to take an action of Hastur’s choice that the creature could ordinarily take as an action on its turn.
• Tattered Lash. Hastur makes a Tattered Lash attack.
• Violent Paranoia. Hastur instils a maddening paranoia in a creature it is aware of. The creature must succeed on a DC 33 Wisdom saving throw or be forced to consider all allies as enemies for 1 hour. The creature still considers Hastur a primary threat, but will not make efforts to avoid injuring its former allies and will actively defend itself if approached. The extremity of this effect should be determined by the creature’s personality and the GM. A creature may attempt a DC 33 Wisdom saving throw at the end of each of its turns, ending the effect on a success.