First created during the Age of Technology, the workings of the Clavis are not fully understood by the Tech-priests of the Adeptus Mechanicus in the late 41st Millennium. But the device interfaces in some way with the wearer's central nervous system so that is can monitor and update him on his vital signs.
The Clavis also acts as a unique and complex key that contains a myriad of Inquisitional override codes, artificially intelligent Machine Spirits and other, more arcane systems that allow it to bypass nearly any technological seal or disrupt any electronic mechanism. The Clavis communicates with light, vibration, and other, less-known means to unseal magnetic locks, energy shields and Void Shield barriers at the Keeper or Watch Master's command. Servitors and other autodefences register the Keeper or Watch Master as a friend and stand down in his presence. The Clavis is what allows a Keeper to walk his vigil undisturbed and reach nearly any secure zone and a Watch Master to command or disrupt nearly any form of Imperial technology.
- Codex Adeptus Astartes - Deathwatch (8th Edition), pp. 30, 66
- Codex Adeptus Astartes - Deathwatch (7th Edition), pp. 33, 74, 107
- Deathwatch - Rites of Battle (RPG), pg. 145