Summary
The skull-and-cog sigil of the Adeptus Mechanicus, signifying the fusion of flesh and machine in service to the Omnissiah.
Lore
The Cog Mechanicum, also rendered Opus Machina (or Machina Opus), is the ancient sigil of the pre-Heresy Mechanicum, the present Adeptus Mechanicus, and the religious faith of the Tech-Priests known as the Cult Mechanicus. It appears upon bulkheads, banners, robes, and war-engines wherever the priesthood treads — a skull-and-cog motif emblazoned on the metal surfaces of the Cult’s holdings.
Symbolism
The device is a hybrid human/cyborg skull set against a black-and-white cogwheel — one half bone, one half machine. The composition declares the central tenet of the Cult: that the slow replacement of organic flesh with bionic substitute is the path toward greater spiritual union with the Omnissiah. The skull names mortality; the cog names the eternal, geared motion of the Machine God.
Sign of the Cog
The Sign of the Cogwheel is the gestural counterpart of the sigil — analogous to the Sign of the Aquila used by the wider Imperium. The fingers of both hands are splayed wide and interlaced, the palms sometimes rolled against one another, so that the meshing fingers mimic the meshing teeth of cogwheels turning in the Omnissiah’s sacred machines. It serves as a neutral greeting or farewell among adepts, and as a token of solemn respect before an honoured machine or a Tech-Priest of unknown rank.