Cult of the Second Son
The Cult of the Second Son is a Genestealer Cult, that infested Necromunda's Hive Secundus and soon gained control of it.
However when the Hive World's Planetary Governor became aware of this, he ordered the rad bombing of Secundus which toppled it to the ground. Afterwards, the area around the fallen Hive's remains was declared quarantine extremis, and the denizens of Necromunda were forbidden from ever talking about it. Unfortuantely for the population of Necronmunda, hundreds of thousands of the Second Son survive, and have become so mutated by the rad bombs, that they have become troglodytes and are now as lethal as Genestealers. Worse still, the Cult has infiltrated the vast tunnel network beneath Necromunda's surface and they attack the Underhive gangs, that foolishly try to raid the remains of Hive Secundus.[1]
Source
- 1: Codex: Genestealer Cults (8th Edition), pg. 17 — The Cult of War