Every Chapter sends a number of its young warriors to Mars where they are trained by the Tech-Priests of the Adeptus Mechanicus. These Marines are inducted into the rites and disciplines of the Machine Mysteries, the secret workings of the Tech-Priests. Once the Marines have completed their training they are no longer simply Space Marines but have also become Tech-Priests and devotees of the Cult of the Machine God. They are skilled in the arcane sciences and dark secrets of technology.

Techmarines do not join the individual Companies but form a separate organisation within the Chapter. This is the Armoury and within its mysterious halls and workshops they constantly work on building and maintaining the Marines' wargear and machines. To their fellow Marines they are mysterious and unsettling figures possessed of disturbing and obscure knowledge and skills.

On the battlefield individual Techmarines are assigned to separate detachments and are tasked with numerous duties. They are capable of effecting battlefield repairs of broken or damaged wargear and are also able to offer observations of the enemy's technology to the commander. They also analyse and record the performance of wargear in battle in order to assess potential improvements that can be made for future conflicts. Lastly they are doughty warriors whose combat effectiveness has proved its worth many times over.

Revilers Techmarine

Ultramarines Techmarine

The Techmarine's uniform and insignia is unusual since it bears only modest reference to the Chapter. All Techmarines, irrespective of Chapter, wear red power armour. Chapter affiliation is displayed on a suitably decorated shoulder pad and the suit will display the Machina Opus badges of a Tech-Priest but otherwise their armour is free of unit, tactical or organisational markings. If there are ranks within the Armoury only the Techmarines are aware of them, and they are habitually secretive of such matters.