Hastur The Unspeakable
Sandy Petersen's Cthulhu Mythos - Pathfinder

Hastur the Unspeakable

CR 21; XP 409,600
CE Great Old One of decadence, disorder, and nihilism
Primary Sources Ambrose Bierce “Haita the Shepherd” and “An Inhabitant of Carcosa”; August Derleth, “The Return of Hastur”


Domains Chaos, Evil, Rune, Void
Subdomains Dark Tapestry, Language, Stars, Wards
Favored Weapon rapier
Symbol the Yellow Sign
Temple manor houses, observatories, playhouses and theaters, standing stones on hilltops
Worshipers decadent nobles, necromancers, nihilists, playwrights, those who have found the Yellow Sign
Servitors byakhee, the King in Yellow, undead

Influence Stage 1 (DC 27)

Area 1-mile radius; Nucleus 0 ft. (always adjacent to viewer)
AC 37; Saves +23; HP 400
Effects psychic assault, quantum reality, spells
Escalation In order to advance to stage 2, Hastur must approach within 10 miles of the influenced area (this occurs automatically after 3d6 hours of the beginning of a stage 1 influence).

Influence Stage 2 (DC 30)

CR 24; XP 1,228,800
Area 2-mile radius; Nucleus 10-ft. square (always adjacent to viewer)
AC 42; Saves +25; HP 520
Effects possession, psychic assault, quantum reality, spells
Escalation In order to advance to stage 3, Hastur must approach within 1 mile of the influenced area (this occurs automatically after 3d6 minutes of the beginning of a stage 2 influence).

Influence Stage 3 (DC 32)

CR 27; XP 3,276,800
Area 4-mile radius; Nucleus 30-ft. square (always adjacent to viewer)
AC 45; Saves +28; HP 640
Effects devastating attack, possession, psychic assault, quantum reality, spells
Escalation In order to advance to stage 4, Hastur must approach within 300 feet of the influenced area (this occurs automatically after 3d6 rounds of the beginning of a stage 3 influence).

Influence Stage 4 (DC 35)

CR 30; XP 9,830,400
Area 16-mile radius; Nucleus 100-ft. square (always adjacent to viewer)
AC 48; Saves +31; HP 760
Effects destruction, devastating attack, possession, psychic assault, quantum reality, spells


Combat Hastur can be defeated through damage, but in order to defeat it, each observer must defeat their own observation of Hastur that appears before them. One cannot interact with a version of Hastur observed by someone else, but one can aid someone else indirectly against their observed Hastur (such as via healing damage or removing debilitating effects). Once all creatures in the area of influence defeat Hastur, the influence ends, provided at least one observer remains standing. If every observer in the influenced area is destroyed by Hastur, it typically departs, although its influence may linger in the area for a few hours, days, years, or more at the GM’s discretion, allowing it to attack anyone who wanders into the area of influence.

Influence Effects

Destruction (Ex) Every time a creature takes hit point damage or suffers ability drain from any of Hastur’s influence effects, that creature must make a successful Fortitude save to resist being instantly slain. This is a death effect.

Devastating Attack (Ex) At the start of the round, Hastur lashes out at all observing targets with its tentacles. Each target must make a successful Reflex save or take 20d10 points of bludgeoning damage. A successful save reduces the damage by half.

Possession (Su) At the start of a creature’s turn, after resolving the effects of Hastur’s psychic assault, the creature must make a successful Fortitude save to resist being physically transformed by Hastur’s presence. A failure indicates the creature takes 1d6 points of Constitution drain. A creature drained to 0 Constitution in this way has any Intelligence, Wisdom, or Charisma damage inflicted via Hastur’s psychic assault immediately cured, but is also transformed into a chaotic evil Mythos undead under Hastur’s control. This is a death effect.

Psychic Assault (Su) At the start of a creature’s turn, it must make a successful Will save or take 1d6 points of ability drain to Intelligence, Wisdom, or Charisma (determined randomly) as Hastur’s presence begins to induce madness and unmake sanity. This is a mind-affecting effect.

Quantum Reality (Su) While all of the Great Old Ones and Outer Gods have unusual effects and strange powers when their influence stains reality, Hastur may be the most complex and bizarre. Hastur embodies a sort of cosmic variation on quantum entanglement. When two particles are entangled, they affect each other regardless of distance between them. Likewise, Hastur affects the observer across unlimited distance. When Hastur establishes influence in an area, all creatures that observe it are in turn observed, and as long as line of sight between Hastur and the observer persists, both Hastur and the observer may interact with each other as if they were adjacent. Once observation is established, breaking line of sight only prevents the observer from being able to affect Hastur—the observer remains adjacent to Hastur as long as his influence persists, even if the observer leaves the area of influence. As a result of this breakdown of reality, since Hastur is always adjacent to the observer, his influence has no speed. No matter how far the observer runs, Hastur remains next to them and can affect them as determined by the stage of his influence.

Spells Hastur can cast a wide range of spells, but typically he limits his choices to a relatively narrow but still devastating selection of them. At the start of each round every creature in the area of influence is targeted by one of the following spells. The effective caster level of the spell is equal to the influence’s current CR. At the GM’s option, other spells may be substituted for the ones below.
d12 Spell Cast
1 phantasmal killer
2 enervation
3 hold monster
4 slay living
5 greater dispel magic
6 harm
7 insanity
8 power word blind
9 temporal stasis
10 power word stun
11 dominate monster
12 power word kill

Hastur is one of the vilest entities even within the Cthulhu Mythos. He is cosmic in origin, and dangerous even to name. His prophet or avatar is the King in Yellow, though it’s not clear exactly what their relationship is, other than that it is a close one.

Hastur himself often appears as a great, boil-covered head bedecked with boneless limbs. The most terrifying aspect of Hastur is that due to his other-dimensional reality, he is effectively present physically wherever he can be seen, regardless of ostensible distance. Of course, Hastur’s disorienting perspective shift is a doubled-edged sword. Not only can Hastur interact with observers physically and instantly at a distance, but an observer can strike back at him with ease.

Hastur’s Sizes

Hastur functions differently at different distances, as the natural laws of perspective would suggest. His influence grows more potent as he descends from the sky where he has been called, and he appears to grow larger as he does so, but the relationship is disconcertingly counter-intuitive. Importantly, his apparent size for anyone who has observed him during this influence is only initially based on the distance between him and the observer. When a character in the area of the influence notices Hastur, Hastur's perverse geometry creates a connection to that observer. For as long as Hastur's influence lasts, his apparent size is thereafter based upon Hastur's shrinking distance from the area of influence. Even if the observer moves away, Hastur appears to be roughly the same size. Indeed, he continues to grow larger as he nears his destination, even if the observer has since moved farther away.

Hastur's growing apparent size can be classified into five dimensional categories (zero-dimensional through fourth-dimensional), as described below.


This is Hastur’s state when he is so far away as to be invisible to the target (for example, at his home at Aldebaran, dozens of light years away). But, because of Hastur’s nature, he is still present and capable of limited interaction with anyone within line of sight of Aldebaran (even if his presence is masked by sunshine). This is why Hastur can be summoned simply by mentioning his name—in a very real sense, he is already there, though of miniscule undetectable size. Once called, he simply enlarges himself at the target site. Of course, in this mode, Hastur is “present” to billions or even trillions of beings, and even a Great Old One cannot pay attention to them all. Still, those who are thinking of Hastur or talking about him tend to draw its attention, and there is always a chance he’ll show up in such a case.


When Hastur is so far away that he appears as a mere dot in the distance, that tiny dot is still able to attract the eye, and is able to make audible sounds and flashes of yellow light. At this stage, his attacks are purely psychic and magical.


When Hastur is too far to exert much physical force (typically a few miles away), he resembles a projected image. This appears to be several feet across and within arm's reach regardless of distance, but cannot exert enough force to attack. At this size, Hastur can still use spells and psychic attacks but can also attempt his possession attack, which causes him to merge with a target and turn it into a scaly, boneless mockery of Hastur. Such a possessed being can continue attacking other nearby targets, though without Hastur’s special distance-defying abilities.


When Hastur is between 300 feet and 1 mile away from his destination, he manifests to each observer as a titanic horror many dozens of feet across. At such a size, Hastur’s relatively small tentacles are now large enough to attack effectively, and Hastur combines them with his other attacks into a devastating barrage of crushing tentacles, possession, psychic attacks, and spells.


Anyone closer than 300 feet to Hastur must bear the full brunt of Hastur’s presence seeming to press in on all sides. Most perish instantly.

Hastur in Combat

Hastur is extraordinarily devastating largely because each foe must fight him individually. He cannot be conventionally outnumbered because everyone observes and must face him separately. For instance, if Hastur appears before an army of a hundred thousand warriors, there ensue a hundred thousand one-on-one fights against the Great Old One, with a predictable outcome. Obviously, Hastur prefers mass battles when he can achieve them.

Each visible Hastur (one per observer) must be defeated individually. When this is accomplished, then there is one fewer Hastur to go around, and the victor can then try to assist another in his own fight. Unfortunately, the victor can no longer observe or interact with Hastur, and so that individual’s efforts can only be to aid a friend indirectly (such as through healing or support magic).

Once everyone in the area has either been destroyed by Hastur or has driven off their personal Hastur, the Great Old One departs. However, if the King in Yellow is present, he can re-awaken Hastur and the process begins again from the start.

Sandy's Notes: Hastur’s Effect On Reality and Perspective

When you look at a tree in the distance, it seems smaller, due to the natural laws governing light and perspective. You can hold your finger and thumb up, and seemingly hold the tree between them.

The difference between normal, sane objects and Hastur is that if Hastur has been awakened and is off in the distance, a person trying to “pinch” Hastur between finger and thumb actually feels Hastur, and more to the point, can interact with him.

Of course the smaller Hastur’s image, the less potent he is. Those who are close to Hastur’s colossal form are immediately swamped by his presence, but those farther away must also battle the Great Old One as if he were simultaneously present within reach. Ordinarily, observation causes a change in the observed target. But when Hastur is being observed, he affects the observer, rather than the other way around.

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