Luna is the ancient moon of Holy Terra, the first world beyond humanity's cradle to be settled and the oldest bastion of the Imperium after Terra itself. Long ago it was home to the gene-wrights of the Selenar, secretive cults who mastered the sculpting of human flesh, and its craters and domes have witnessed the whole span of human spaceflight since the dawn of the species.
In the age of the Imperium, Luna serves as a fortress and a shipyard, its surface studded with void-docks, defensive batteries, and the great installations that help guard the approaches to the Throneworld. It was here, in humanity's earliest ventures, that some of the first warriors of the Emperor's grand design were raised, and the moon retains a place of honor and strategic weight in the defense of the Sol System.
Among its fastnesses stands the citadel of the Sisters of Silence, the null-souled sisterhood bound to the guardianship of Terra alongside the Adeptus Custodes. Luna's long history has made it a place of secrets as much as strength, its vaults holding relics and knowledge from the Imperium's founding. Silent and watchful, the old moon endures at humanity's very heart, forever circling the world it was first colonized to serve.