The Disciples of Lydia are an old and proud Space Marine Chapter based in the Lydia system. Founded in M34, their history is long and complex, and closely intertwined with the history of the Lydia system itself. They are renowned for showing an almost territorial devotion to the people of the Lydia system, interrogating and inspecting any Imperial vessels that pass through there, which has in the past caused friction with other Imperial Institutions. However, the suspicion with which they regard outsiders from the Imperium is magnified a thousandfold when they encounter non-human vessels, and any xenos coming near the Lydia system can expect to be engaged on sight without warning.