Most Space Marine Chapters have a Master of the Forge: the most senior Techmarine within the Chapter. With deep understanding of the arcane sciences refined over many standard years of experience, the Master of the Forge is comparable to a Tech-priest of the Adeptus Mechanicus. The Dark Angels maintain a similar role within their Chapter known as the Master of the Rock, although there is an ominous difference.
Upon ascending to the honoured position, the Master of the Rock follows his predecessors in the office by being permanently and cybernetically hard-wired into the control nave of Cogitators located deep within the asteroid base that serves as the Dark Angels' mobile fortress-monastery.
It is his mind alone that perceives the workings of the force field that still shields the asteroid base. The previous Masters of the Rock, whose bodies of flesh and bone have withered, are left in place, their mechanical upgrades still functioning while their bones fall in dusty heaps below. Eventually, these bodies will be collected for display in the Alcoves of Honour.
Because of their dual allegiance to the Chapter and the Adeptus Mechanicus, Techmarines are never inducted into the Deathwing. This includes the Master of the Rock; he is privy only to the secrets of the Dark Angels' asteroid base and its hoard of ancient technology, but never to the greatest secrets shrouding the Chapter's origins.
- Codex Adeptus Astartes - Dark Angels (7th Edition) (Digital Edition), "Chapter Organization"
- Codex Adeptus Astartes - Dark Angels (8th Edition), pp. 13, 23, 26