Sketch of an adult Psychneuein made by a Magos Biologis of the Adeptus Mechanicus.

Psychneuein are insectoid creatures native to the Immaterium that resemble huge, spindly wasps.

Thankfully rare, Psychneuein are vile Warp entities drawn to the mental emanations of unprotected, badly-injured or nascent psykers whose minds they attack for the obscene purpose of gestating their progeny.

Psychneuein have been known to evidence various distinct genera, of which three have been identified -- the Mara Strain, the Luctos Strain and the long-extinct Prospero Strain.


Mara Strain

Of the known genera of the Psychneuein identified by Imperial scholars, the Mara Strain is deemed the most dangerous. The Mara Strain was first identified by Ordo Xenos Inquisitor Ark-Ashtyn during a heavy infestation at the mining penitentiary on the Ice World of Mara in the Calixis Sector, in the 6th century of the 41st Millennium.

Although the Mara facility was subsequently decommissioned, the tale of the "ice station massacre" remains a favourite dark fable among the sector's spacefarers.

Since then, confirmed incidents of Mara Strain infection have occurred on the Calixis Sector worlds of Dusk, Lachrymae and Pellucida V as well as several vessels transiting near Mara, although these incidences remain thankfully very few.

Luctos Strain Psychneuein

A rare but terrible form of Warp entity, Psychneuein represent well the perils of the unprotected psyker. Their capacity to spread and overwhelm civilised areas, in spite of a lack of any apparent intellect, is horrifying to observe, and signs of Psychneuein infestation are treated seriously by the Inquisition.

The Luctos Strain, identified in 281.M39 by Brother Epistolary Arno Tannis of the Deathwatch in the Jericho Reach, seems particularly resistant to extinction, having reappeared dozens of times after seemingly being annihilated.

Tannis himself was slain by larval infestation less than a day after making his report of a successful mission against them to the Watch Commander, forcing Watch Fortress Erioch into lockdown until the creatures could be contained and purged.

Prospero Strain

The second strain of Psychneuein positively identified by the Ordo Xenos is the long-extinct Prospero Strain that resided on the now barren homeworld of the Thousand Sons Space Marine Legion. These creatures were also insectoid and utterly repellent to the human eye.

Prospero's ancient capital city of Tizca was the last outpost of human civilisation on that world, after its prior society had been wiped out thousands of standard years ago by the predations of the Psychneuein. Tizca was a city where the survivors of a planet-wide cataclysm found refuge from the assault of the Psychneuein.

The Thousand Sons always suspected some freak upsurge in the Warp triggered an explosion of uncontrolled psychic potential within the Prosperine population, driving the Psychneuein into a reproductive feeding frenzy. The civilisation of Prospero collapsed and the survivors fled to the city in the mountains.

For thousands of Terran years, the people of Tizca endured, while all they had built in the millennia since leaving Terra fell to dust. The surface of Prospero was dotted with the remains of their dead culture. Empty cities were overgrown with forests and vines, the palaces of their kings overrun with wild beasts.

The survivors survived by salvaging knowledge and equipment from the destruction to construct techno-psychic arrays and sustainable energy sources, which then allowed them to build giant hydroponic gardens deep in the caverns of the ventral mountain ranges. They survived the Psychneuein threat by further developing the very psychic powers that made them so vulnerable.

The Psychneuein were drawn to Tizca in their thousands, but the survivors were able to train their most gifted psykers to use their minds to erect invisible barriers of pure thought (known as "kine-shields"). They were primitive, bombastic powers compared to the subtle arts later employed by the Thousand Sons, but they kept the creatures at bay. Even so, the practitioners of the mysteries remained locked in their limited understanding of the Immaterium's power until the coming of the Thousand Sons' Primarch Magnus the Red.

When Magnus came to Prospero, it was said that a great comet had borne him to the ground, for the impact he had on them was as great as his impact upon the planet's crust. The Tizcan commune, which was the name the survivors of the Psychneuein assault on Prospero gave to their little enclave, was a place rooted in tradition, but they had some skill in wielding the power of the Immaterium.

Of course, they did not know it by that name, and the powers they had, while enough to keep the psy-predators at bay, were little more than the enchantments of idiot children. The young Primarch was schooled in the ways of the commune, and he quickly learned everything they had to teach.

In truth, Magnus had outstripped the learning of their greatest scholars within a standard year of his arrival. Their teachings were too dogmatic, too linear and too limiting for the potential of a Primarch's mind. His intellect was superior in every way to those that taught him. With his teachings, he knew they could be so much more.

To increase his understanding of his powerful psychic abilities, Magnus took a walk into the desolation of Prospero. True power comes only to those who have fully tested themselves against their greatest fears. Within the commune, the Primarch knew no fear, no hunger or want and had no drive to push his abilities to their full potential.

Magnus needed to be tested to the very limits of his powers to see if he even had limits. Out in the wilds, Magnus knew he would either find the key to fully unlock his powers or die in the attempt. A year after his coming to Prospero, the Primarch walked from the gates of Tizca and marched into the wilderness for nearly forty solar days.

Through his observations, Magnus learned to harness his powerful abilities during his long trek. He also met Amon, the future Captain of the 9th Fellowship. Despite their discoveries, as was the way of history, nothing of import was ever achieved without bloodshed. Tragedy soon struck Tizca in the form of the return of the Psychneuein menace.

Temporaily lax in their mental discipline, the Psychneuein were drawn to the large commune of psykers in Tizca in their thousands, blackening the sky with their numbers as they descended like a plague from ancient times. They swarmed from their darkened caves, organically shifting clouds of deadly clades, the relentless buzzing of thousands of crystalline wings representing the sound of inevitable doom.

The males swarmed in, a hurricane of snapping mandibles and tearing claws, and fifty men died in the time it takes to draw breath. Behind the males came the females, engorged with clutch upon clutch of immaterial eggs. Their furious reproductive hunger was insatiable, and dozens of the Primarch's friends fell to their knees in horror as they felt the psychneuein eggs take root in their brains.

The beasts swirled around them, battering the Prosperines with psychic thrusts, scrabbling at their mental barriers to seed their minds with their eggs, and only the strongest of them remained. Amon and eight of the masters of Tizca stood with the Primarch, and as the Psychneuein attacked again, Magnus knew this was what he had been seeking all along, a true test of his abilities. He would finally discover whether he had limits. Magnus would see if he was the master of his powers or was to be found wanting.

As the Psychneuein came at the Prosperine defenders again, something magnificent happened. The Primarch felt something move within him, feeling changed, as though an immense power that had lain within him, dormant and untapped, surged to life. As Magnus contemplated the moment of his death, raging fires erupted from his hands.

The Primarch hurled torrents of flame into the sky, as though he had always known he had such powers, and smote hundreds of Psychneuein to ruin with every gesture. Soon, the other Tizca masters displayed hence-unknown abilities as well, as walls of flame sprang up at their command. Others were able to pluck beasts from the air and dash them on the rocks with the power of their minds. Still other defenders were able to will the vital fluids within the Psychneuein to boil within their exo-skeletons.

Amon saw images of the future and imminent danger seared though his mind, and he cried words of warning to his fellows, telling them of dangers to come and of how they might avoid them. Some of the other defenders sensed the lust within the Psychneuein to plant their psychic seed within the humans' minds, the relentless animal hunger that drove them to feed and propagate. They reached into the minds of the beasts and twisted their perceptions so that they became blind to the humans.

With these newfound abilities, the later psychic Cults of the Thousand Sons Legion were born. The threat of the Prospero Strain of Psychneuein was forever after rendered inert.

Anatomy and Physiology

Psychneuein are foul but powerful psychic creatures that normally reside in the Immaterium. These insectoids have plagued Mankind since at least the Age of Strife, when there was an explosion of psychic abilities amongst the various populations of humanity across the galaxy.

What makes this creature so dangerous is its reproductive cycle. The female Psychneuein is drawn to psychic emanations in realspace and has a rudimentary fusion of telepathic and telekinetic powers. When fertile, the female psychically projects a clutch of its eggs into the brain of a psychically-active host being with an unprotected mind, vulnerable to the power of the aether.

The eggs are small, no larger than a grain of sand, but by morning the following day, they will hatch and begin to feed on the host's brain. At first the victim feels nothing more than a mild headache, but by afternoon he will be in agony, raving and insane, as his brain is devoured from the inside out.

By nightfall, he will be dead, his skull a writhing mass of plump maggots. In the space of a few solar hours, the grubs have picked the carcass clean and will seek a dark place to hide in which to pupate. By the following day, they will emerge as adults, ready to hunt and reproduce.

Once infected by a Psychneuein, a psyker slowly loses intelligence and his or her appearance slowly changes until they are either killed by the emerging Psychneuein larvae or their instability unleashes other psychic perils, such as insanity or even daemonic possession.

Psychneuein of both strains have three well-known phases of their life cycle -- the larval phase, the adult phase and the "infected" phase. Larval Psychneuein are typically puny creatures, whose main strength is their ability to infect others.

Injuries can trigger a sudden metamorphosis to its adult form. Their small size makes them easy to kill but they usually occur in large numbers, making an infestation of Psychneuein difficult to control, particularly if there are any latent psykers around for them to infect.

Once in adult form, the Psychneuein are relatively easy to destroy, having no compulsion to hide. However, they are still dangerous because they are capable of breeding more of their kind within the minds of nearby unprotected psykers. Over short distances (of up to 100 metres) all psykers are vulnerable whether protected or not.

The adult Psychneuein is vividly coloured in yellow and black, its wings are transparent. Grubs are white and generally maggot-like in appearance, though Psychneuein of the Mara Strain are said to resemble spiny grubs. The adult is two-and-a-half metres long, grubs reach a maximum size of a half-metre before they pupate.

Adult Psychneuein are much more dangerous than their larval brethren: they are stronger, faster, tougher, and more perceptive than humans and capable of flight, turning insubstantial, and detecting minds. A single adult Psychneuein is a significant threat to any and every nearby sentient being.

Forms of Psychneueins

  • Psychneuein Grub - Psychneuein grubs are typically around a metre long and ooze a greyish mucous as they crawl. They are unsettling to behold, as if their motions are out of synch with the reality they are spawned into, and few beings can stomach their presence for long. Clutches of Psychneuein grubs are more inclined to hide in some dark corner, safe from aggressors. It takes relatively little time for grubs to mature into full-grown Psychneuein, but they are extremely vulnerable to aggressors until that time.
  • Psychneuein Drone - Making up the overwhelming majority of adult Psychneuein, drones resemble giant wasps, each two metres long from their mandibles to the end of their thorax. Capable of swift movement and extremely strong and resilient, Psychneuein are also innately psychic and venomous. Their stingers can pierce any armour wrought by man or Daemon, and in significant numbers they can overwhelm even the mightiest of warriors. Within the confines of a Space Hulk, swarms of Psychneuein drones cluster in vast caverns and abandoned vaults, emerging to hunt periodically. The sound of their droning flight has been known to infect the minds of men and drive them to madness, and it is this sound that most often heralds their hunting swarms.
  • Psychneuein Queen - Thankfully rare, it is posited by the Magos Biologis scholars of the Deathwatch that the Psychneuein breeds that they have titled “queens” require special conditions to create. The special circumstances that are necessary for a grub to become a queen instead of a drone have never been replicated. However, those rare few that have been encountered were sighted aboard the Space Hulk Mortis Thule. These beasts are extremely dangerous, not only for their enormous size and ferocious manner, but also for their ability to spread their vile brood across the stars. Large, bloated, potently psychic, and extremely strong and resilient, a Psychneuein queen is a deadly foe, the kind of creature that only the mightiest and most resolute warriors can hope to combat.



Warhammer 40,000 Grim Dark Lore Part 14 – A Thousand Sons


  • Dark Heresy: Core Rulebook (RPG), pg. 353
  • Deathwatch: Ark of Lost Souls (RPG), pp, 134-136
  • Warhammer 40,000: Rogue Trader Rulebook (1st Edition), pg. 205
  • A Thousand Sons (Novel) by Graham McNeill, pp. 135-136, 139, 141-142, 186-190
  • Scars (Collector's Edition Novel) by Chris Wraight, pp. 142, 149-153, 178, 182-183
Raven Rock Videos
Warhammer 40,000 Overview Grim Dark Lore Teaser TrailerPart 1: ExodusPart 2: The Golden AgePart 3: Old NightPart 4: Rise of the EmperorPart 5: UnityPart 6: Lords of MarsPart 7: The Machine GodPart 8: ImperiumPart 9: The Fall of the AeldariPart 10: Gods and DaemonsPart 11: Great Crusade BeginsPart 12: The Son of StrifePart 13: Lost and FoundPart 14: A Thousand SonsPart 15: Bearer of the WordPart 16: The Perfect CityPart 17: Triumph at UllanorPart 18: Return to TerraPart 19: Council of NikaeaPart 20: Serpent in the GardenPart 21: Horus FallingPart 22: TraitorsPart 23: Folly of MagnusPart 24: Dark GambitsPart 25: HeresyPart 26: Flight of the EisensteinPart 27: MassacrePart 28: Requiem for a DreamPart 29: The SiegePart 30: Imperium InvictusPart 31: The Age of RebirthPart 32: The Rise of AbaddonPart 33: Saints and BeastsPart 34: InterregnumPart 35: Age of ApostasyPart 36: The Great DevourerPart 37: The Time of EndingPart 38: The 13th Black CrusadePart 39: ResurrectionPart 40: Indomitus
Community content is available under CC-BY-SA unless otherwise noted.