A somber cemeery world of the Drusus Marches, Cryptus is devoted entirely to the interment and veneration of the dead. Its surface is a patchwork of tomb-cities and ossuary cathedrals, so much so that “a trip to Cryptus” has become a sector euphemism for death.
Among its sacred sites stands the ruined Sanctified Glass Cathedral, once famed for warp-resistant glass later repurposed into Cryptus Shotgun Shells, munitions deadly to daemons. The world is maintained by Sororitas orders, servitors, and penitents, with pilgrims arriving for memorial rites. It is not a place of industry, but of memory, guardianship, and the eternal silence of the Imperium’s fallen.
Ignis Aeternus WH 40K campaign notes 