One by one you have made your way down into the underhive of the massive capital spire of Hive Desoleum. You've descended through the crowds of stinking thrall workers on their endless parade of shifts and past Ministorum processions of screaming flagellants towards levels of the hive that have not seen the light of day in thousands of years. The lingering odor of blood and the stench of the massive press of humanity that is the manifest of the Emperor's divine will clings to your clothes as the heat of ancient machines who's function is long lost heats the air oppressively all around you.
Your mind flickers back to the cryptic message delivered by gene-coded servo-skulls as you enter the semi-abandoned hab block: You have been called once again to the Emperor's service. As the last of you arrive in the secure bolt hole you see the others: The Scribe, the Assassin, the Arbitor, the Infiltrator, the Outcast. In one corner of the dim candle lit room you see a dull glow and flickers of movement in the candlelight indicating the Tech-Chiurgeon is communing with his servo-skull.
Moments after the last of you arrives a panel in the wall slides away revealing the emaciated body of a lobotomized servitor. Dry dust fills the air and cobwebs rip audibly as the ancient automaton takes several steps to the center of the room. The servitor's tarnished vox unit crackles with static before a mechanical voice intones:
"Hive Desoleum holds many heresies and horrors, and you my acolytes are gathered here for but one of them. There are increasing reports of horrible deaths within the hive's upper levels, with odd items of a possible xenos or archaeotech nature found with each corpse. Some of nobles have related that these deaths were preceded by bouts of erratic and troublesome behavior and rumors have swirled of late that a hive noble named Lans Guljian has exhibited many of the same behaviors.
Rejoice for you are tasked with the Emperor's Work: to investigate the deaths and possible connections to any illicit artifacts, determine if they are potential dangers of a wider nature, and terminate their distribution. Recover and contain any items uncovered, lest they corrupt others.
Carry the Emperor's Light with you through the hive, for there is little proper illumination to be found in this festering, ancient edifice. Desoleum teeters on the blade's edge of damnation and one further heresy could topple the entire hive into the abyss. May you have the honor of dying in His service."
With a hiss the servitor's flesh begins to rapidly disintegrate, falling to the floor in hissing rivulets. After only a few moments, all that remains is a pool of sizzling gore and a pile of servitor compellers cracked with age.