The Cog Mechanicum, also called the Opus Machina, is the ancient symbol used to represent the pre-Horus Heresy Mechanicum, the present Adeptus Mechanicus and their religious faith, the Cult Mechanicus.
The emblem, a hybrid human/cyborg skull in front of a mechanical cog, represents the fusion of human flesh with machine that is the goal of every Mechanicus Adept.
The members of the Mechanicus believe that slowly replacing portions of their organic bodies with more "pure" bionic replacements leads to a greater spiritual union with the Omnissiah, the Machine God who represents the sum total of all knowledge in the universe.
- Codex Imperialis (2nd Edition)
- Warhammer 40,000 Rulebook (5th Edition)
- Mechanicum (Novel) by Graham MacNeill