Prequel to Crusade
The Adeptus Mechanicus, known also as the Priesthood of Mars, The Machine Cult or the Mechanicum is a technocratic organization that preserves the ancient technology that the Imperium is utterly reliant upon yet understands so little about. For this reason alone, the Mechanicus has a near-unique level of autonomy within the Imperium because of their monopoly over technology – they control their own fiefdoms, Forge Worlds, where their machine-worshiping religion replaces the more traditional Imperial cult.
Created by human’s who settled the fourth planet of the Sol System, Mars, the Mechanicum flourished in the early days of human expansion into the stars, founding the ancient Martian Empire. When the Imperium was founded the Emperor forged an alliance with the Mechanicum ensuring peace between the two empires, and the supply of goods to the new Emperor’s forces. But the defection of the leadership of the Martian Empire to the service of the traitor Horus during the Imperium’s civil war, and the subsequent Martial Civil War almost destroyed the Martian Empire.
In the wake of the Heresy, the loyal Mechanicum were absorbed into the Imperium as the Adeptus Mechanicus, sacrificing a modicium of freedom in order to placate the reeling Imperium. This decision has been the cause of many internal disagreements among the Machine Cult – and is the reason why the Imperium has not made any attempt to stamp out their divergent belief in an ‘Omnissiah’ a ‘machine god’ that some associate with the God-Emperor and others believe to be a greater deity, or a state of being.