Deimos is the lesser moon of Mars, a scarred and airless rock that has served the Adeptus Mechanicus since the earliest days of humanity's expansion into the void. Where its sister moon and the Red Planet below teem with the labours of the Machine Cult, Deimos has long held a quieter, more secretive purpose, its cratered surface concealing sealed vaults, orbital yards and forge-shrines of great antiquity.
The Priesthood of Mars regards even this barren moon as holy ground, for it orbits the sacred forge-world that is the heart of their faith. Beneath its dust lie machineries whose function has been half-forgotten, tended by tech-priests who chant the rites of maintenance over mechanisms older than living memory. Nothing on Deimos is ever truly discarded, only sanctified and set aside against some distant need.
Through the long millennia Deimos has watched over Mars as a silent sentinel, its guns and stations woven into the defence of the Sol System. To set foot upon it without sanction is to invite death, for the Mechanicus guards its secrets jealously. In the grim shadow of the 41st Millennium it endures as it always has, a small cold moon burdened with the weight of ten thousand years of the Machine God's mysteries.