NHCC Dark Heresy
The Adeptus Mechanicus is the official name for the Cult Mechanicus or Cult of the Machine. They acknowledge the Emperor as the ruler of the Imperial Cult or the Ecclesiarchy. Instead, they follow their own dark and mysterious scriptures.
They believe knowledge is the manifestation of divinity, and all creatures and artifacts that embody knowledge are holy because of it. The Emperor is the supreme object of worship because he comprehends so much. The Adeptus Mechanicus also regard flesh as weak and view the removal and replacement of biological with mechanical parts sacred. Most elder tech-priests have few organic parts left and are more machine than man.
The Adeptus Mechanicus is based on Mars and they are the sole rulers of the planet. They provide the technical experts of the Imperium and field armies of Titans and knights.