In The Crush of the Hive, Part 3

Lacking further clues, the acolytes chose to investigate the Underhive. Joined by a mendicant Techpriest, they travelled into the depths and followed a psychic trace to a hidden shrine of the Illuminated Brethren. The keeper of this shrine was an old woman named Matron Rho, who they recognised as being a scion of the Amaranth family. In the shrine was a statue containing the skull of her father, Cius Amaranth.

Rho explained that when the family chapel was defiled by 'men with flamers', she and her father fled. Her father died, but she enshrined his skull and cyber-eye here. She also mentioned that a nice man named 'Falco' often visited the shrine, and that the cyber-eye of her father was stolen after one of her visits.

Unfortunately, the acolytes let slip that they worked for the Inquisition, and Rho attacked them. As they fled the burning shrine, they were attacked again by the Mushers, and sustained considerable wounds as they retreated to the upper hive. There, they found a scene of carnage. Rioting had begun in the Basilica of the Founding and spread across Constanthus Hive. The acolytes travelled to the Basilica, where they discovered hundreds of thousands dead. The Amaranth crypt had been broken into, and the Illuminated Brethren - led by a man with a cybereye - were conducting a bizarre ritual.

The acolytes were unable to stop the ritual, but they were able to capture the cult leader as the Imperial Guard turned their guns on the Mushers, and blood and fire consumed the sanctity of the ancient basilica...