Keeper

"Now tell me whatever secret you're holding you Elf Bitch before I turn your ass into my glaive sharpening tool."

The Deathwatch's Keepers are Space Marines attached to the Deathwatch, the Chamber Militant of the Ordo Xenos of the Inquisition. Where most Space Marines who serve with the Deathwatch eventually return to their parent Chapters, the Keepers' service is for life. Hardcore.

Overview

These Space Marines are mostly seen on Watch Fortresses, standing watch over forbidden areas of the installations; their job boils down to yelling "By order of the Jarl Deathwatch, stop right there!" at anyone trying to get into these areas then pushing a glaive up their ass if they refuse to comply. The reason why is because these areas are where the 'Watch stores captured Xenos prisoners for 'interrogation' and 'experiments', along with the occasional artefact.

Uniquely among the Deathwatch, their duty is held to such heights that even Inquisitors are unable to pass a Keeper without authorization from the Watch Commander. Yes, you hear us right, the nigh-omnipotent Inquisition has to ask for permission to even get past a Keeper. Awesome.

Thanks to the inherent mental pressures of guarding xeno prisoners and doomsday devices (both Imperial and xenos) in the middle of fucking nowhere, with no chance of ever returning to your Chapter, the selection process is extremely harsh (even by SM standards). To start with, the Marine needs to have served a decade-long watch with a clear record of good service (escorting Kill Teams, capturing/guarding xeno prisoners, etc.) to be considered at all; if they pass this, they get questioned by the Watch Commander and his advisors while being mind-raped by at least one Librarian, to uncover any mental flaws or lack of determination.

Assuming the prospective Keeper doesn't go completely bonkers or just drop dead from a brain hemorrhage, he gets put through a initiation ceremony involves undertaking terrible and binding oaths to protect the Deathwatch's secrets above all else. At the height of this, a shiny little Archaeotech vambrace known as the Clavis is locked onto his right arm to permanently (both physically and symbolically) bind him to his new duties. This little device essentially lets him control the whole of the Watch Fortress's systems at will, and even semi-control the machine spirit of a whole goddamn ship.

Despite what you might think, becoming a Keeper does not necessarily prevent assignment to a Kill-Team, primarily because their decades of experience are too valuable for them to remain on perpetual guard duty. To avert any chance of losing control of the Fortress because some xeno bitch decided to Blud Rehvens the Keeper's arm, the Clavis is disconnected from his armor prior to the mission (and it's linked to his vitals anyway, so no-one else can use it and it locks itself when the user dies).

While onboard the Watch Fortresses, they tend to be equipped with ceremonial weapons and armour as a sign of their status - this includes stuff like the page image's power glaive, double-bladed chain weapons, or even ancient las-lances (which may be derived from the Eldar weapon of similar name, or a motherfucking lightsaber pike). They also wear specially-embroidered robes and a lot of High Gothic sigils, because apparently the rare armor and Clavis weren't obvious enough signs of status.