The Forge Worlds are the great industrial planets of the Adeptus Mechanicus, the manufacturing bastions upon which the entire war machine of the Imperium depends. Scattered across the galaxy in their thousands, these smog-wreathed worlds are given over wholly to production, their surfaces buried beneath manufactorums, refineries, and the ceaseless labor of the tech-priesthood.
Each forge world is a domain unto itself, ruled by a Fabricator and his magi rather than by ordinary Imperial governors, and bound to the wider Imperium by ancient treaty rather than direct command. The greatest among them, chief of which is sacred Mars, hold the holy patterns for the most complex and powerful machines of war, and their output can determine the fortunes of entire crusades. They maintain their own armies of skitarii, their own fleets, and their own jealously guarded stores of knowledge from ages past.
Together the forge worlds form the industrial spine of the Imperium, producing the weapons, armor, vehicles, and munitions without which its endless wars could not be fought. Their loyalty is to the Machine God first and the Emperor second, an arrangement that grants them extraordinary autonomy and influence. Grim, hierarchical, and wreathed in perpetual smoke, these worlds are the workshops where humanity's survival is forged anew each day, temples of industry where labor itself is an act of worship.