New Gidlam is an Imperial Hive World located on the outskirts of the Segmentum Solar. It is dominated by thirteen vast hive cities, twelve of which came under the control of the Genestealer Cult known as the Hivecult. Only the thirteenth, Hive Tharanex, remained free of the infestation, though it was under constant assault from the Genestealer Cult's subterranean forces.
At some point in the late 41st Millennium, the cult finally rose up against Imperial rule but the rebellion was successfully put down by the Imperial military.
The genesis infestation of the Hivecult is a prime example of a Genestealer infection that spread like wildfire across a densely populated Imperial planet. That planet is New Gidlam, a Hive World that has thirteen ancient hive cities upon its pollution-blasted surface.
Each of these vast, man-made mountains harbours tens of billions of souls, and all bar one has been conquered by the Hivecult. Only Hive Tharanex holds out, its lessons learnt at the expense of every other population centre. Even then its lower levels are constantly besieged, and its future looks bleak indeed.
The cult's emergence on New Gidlam began with a spate of ritual killings. A warlike underhive family had sprung up around a brood of Purestrain Genestealers. These xenos specimens were originally purchased from a self-appointed "xeno-tzar" known as Deinosis the Great Curator. They were later smuggled into the hive city by furtive gangers looking for a secret weapon to use against their enemies.
Brought swiftly into the sway of the Genestealer they called the "First Father," the gangers went on the warpath, and soon surpassed their rivals. Rather than the traditional route of infiltrating, kidnapping, blackmailing and stealing from their enemies to grow slowly in the darkness, the cultists went straight for the throat.
They slaughtered one rival gang after another, taking over large swathes of the area known as the Sump. The more dominant gangs that had established themselves in these lower levels saw what was happening and eventually put aside their differences to defend against the Hivecult, but faced with the First Father and his sharp-eyed Genestealers, who could squeeze through narrow pipes and swim across lakes of toxic spill to attack from unexpected angles, the gangers were overmatched.
In the meantime, the aristocracy of the hive city had also been infected by the cult's savage ambition. Its Magus, Vockor Mai, was at the centre of this operation. He brought the ruling dynasties into line one by one, swaying them with his psychic influence and uncanny charisma. There was one, however -- a rich hiver named Thorne who habitually wore a helm of xenos design -- who did not fall to his wiles. In the hours of darkness, Vockor Mai shucked off his robes and assassinated Thorne whilst he was in his bathhouse, cutting the dignitary's throat with the razor-sharp symbol of the cult and leaving it as his calling card.
It was the first of many such kills, each part of a wider initiative to remove obstacles from Mai's path. Though often half seen in the darkness, he was never caught.
With those first acts of killing, the urban myth of the "White Creeper" was born amongst New Gidlam's aristocrats. When the cult grew large enough to spawn the Neophyte Hybrid assassin known as a Sanctus, Vockor Mai bade the operative to go into the hive spires and kill those too intractable -- or too psychically powerful -- to fall to his wiles.
The legend of the White Creeper grew, and spread from hive to hive, though in truth it was several individuals working in concert. Over time, gene-sects were established in twelve of the thirteen ancient hive cities -- but the spread of the cult did not stop there.
New Gidlam's principal human exports -- skilled roachworm silkers and recruits for the Astra Militarum -- spread the infection of the Hivecult from the outer worlds of the Segmentum Solar to its heartlands. With many Imperial Guard regiments recruiting from the gangers of those worlds, the Hivecult spread ever further.
Hidden gang signs and electoos worn under the skin enabled those who owed allegiance to the New Gidlam dynasty to identify one another in secret, and spread their creed in the endless solar hours of inactivity that typified life between engagements for an Astra Militarum unit. The sheer vastness of the Astra Militarum -- and the desperate intensity of the wars they fought -- helped the Hivecult to evade the suspicions of the Commissariat in nearly every conflict zone they infiltrated.
The Hivecult present on New Gidlam eventually launched its great uprising, but its forces were defeated by an Imperial military intervention, which restored order to the planet. While the fate of the cult on the world of its genesis infestation is unknown, the broods of the Hivecult have now spread to many other inhabited planets in Imperial space.
- Codex: Genestealer Cults (8th Edition), pp. 22-23
- Codex: Genestealer Cults (7th Edition), pp. 18, 46
- Planetary Onslaught (7th Edition), pg. 52