Dark Heresy. You are the retinue of Inquisitor Lord Zane Castis, the oldest Inquisitor in the Calixis Sector. His purview is heretical documents, which — for centuries — he has collected from the hands of those who would misuse them. Generally not peacefully.
All such documents are stored in the vast ship Tabularium Bibluvio, which also serves as Inquisitor Lord Castis’ headquarters. It is a sphere, dwarfing lesser ships. The heretical archive is contained in the featureless top half of the sphere; below that, the sphere is hollow for half of the bottom hemisphere, with four mighty black pylons connecting the archive to the living quarters which make up the bottom quarter of the sphere. Shuttles and other such less important spacecraft dock on the top of the living quarters.
Over the centuries, the weight of such a convocation of Chaos and lies has literally warped the space around it. It is deeply unsafe to venture into the archive; at present, Inquisitor Lord Castis affords no other person that right. He himself communes with the texts therein on a regular basis, in order “to keep them under control.” From time to time, horrendous monsters rage down the pylons to assault the remainder of the ship. One of your duties is defense against these unfortunate but inevitable results of the ship’s mission.
Your second duty is to assist your Inquisitor in confiscating more documents. The flow is never ending. Vigilance is paramount. This duty takes you to the foulest slums of the Sector, and also to the most lovely nests of corruption. Chaos knows well how to wear a harmless face. Inquisitor Lord Castis is known for his lack of mercy towards nobility who hope to conceal their heretical studies from him.
Your third and final duty, as given to you a few months ago when you were sent to serve Inquisitor Lord Castis, is to watch him. Eventually, he will bend and break under the strain of the archive. You cannot, of course, hope to defeat an Imperial Inquisitor: the Calixis Conclave merely hopes that, in the event of a catastrophe, you will be able to get out word before your death.
Best of luck.