Cult of the Children
The Cult of the Children was a religious group on Darvon VI, founded by a former Assistant Navigator, Sirval. It was a cloak for a Genestealer Cult which later brought the planet under its control. Sirval had been infected by a genestealer, after which he retired from space travel, settling on Darvon VI, marrying and having children.
The tenets of the cult promoted modesty and hard work, but also complete seclusion from the rest of society, and forbid its followers from travelling off planet. As much of the population were members of the cult, the planet couldn't fulfill its obligation of raising regiments for the Imperial Guard. When a recruiting force of Ogryns descended on the cult's isolated settlements, the cult finally began its uprising, eventually bringing the entire planet under its control.
The Assistant Navigator Sirval was the only survivor of the space freighter Tantalus III which was attacked en route to the Imperial world of Darvon VI. The freighter was boarded by Genestealers and Genestealer Hybrids. Sirval was spared to become a host, and infected by a Genestealer. He was later rescued in a lifeboat in orbit around the gas giant Darvon VIII. Sirval told his rescuers that the Tantalus was attacked by pirates.
The rescuers' shuttle took Sirval to Darvon VI. It towed the lifeboat back to the planet with them, the shuttle's captain planning to claim salvage rights. Sirval was subjected to rigorous examination. Because the Inquisition concluded Sirval showed no signs of spiritual pollution, he was released.
The lifeboat was to be brought down to the planet's space port. However, during the journey to the planet's surface, contact with the pilot was lost. Shortly afterwards the lifeboat crash landed in a dense forest. A purestrain genestealer had presumably killed the crew, and survived the crash landing on the planet.
Three months later, Sirval married a young woman from the city, moved out of town and began homesteading fifteen miles from the site of the crash. A year later, their first child was born.
Subsequently he founded the Cult of the Children, a new religious group; its tenets promoted modesty, industry, and complete seclusion. The cult grew inexorably in power and number until it became the second most popular religion on the planet. Most of the cultists were innocent dupes, completely unaware of the sinister origins of the cult and its even more frightening objectives. However, innocent or not, their number gave the cult a great deal of power on the lightly populated planet. Despite the cult's growing strength, the government did not recognize them as a threat.
It was tolerated, and even seen as beneficial, because its tenets included assent to worldly authority, ("Render unto the Emperor what is the Emperor's"). The Governor did not begrudge the cultists their peculiarities - if the members wished to stay in seclusion or travel about in black, voluminous robes, as long as they paid their taxes, that was their business.
The "religion" of course was nothing more than a genestealer cult, bent on complete dominance, and the planet was overrun and taken over by the cult.
- Space Hulk (Game) first edition, Background book