This article concerns the Grey Knights' homeworld; for the Adeptus Mechanicus' combat walkers see Titan.
Titan is the largest moon of the gas giant Saturn in the Sol System and is wholly controlled by the Grey Knights Chapter of psychically-active Space Marines who serve as the Chamber Militant of the Inquisition's Ordo Malleus. The fortress-monastery of the Grey Knights is based on Titan, and is carved entirely of basalt. Within the fortress hang pennants, banners and flags commemorating the victories and sacrifices made by the Chapter in their eternal war against the daemons of Chaos, but none other than the Grey Knights would recognise the names of these campaigns. The Chapter operates in oppressive secrecy, beyond the knowledge of the Adeptus Terra and even of the Imperium of Man's ruling High Lords of Terra; as a part of the Ordo Malleus, the Grey Knights are answerable only to the Inquisitor Lords of the Ordo Malleus and the Emperor of Mankind himself. Even the location of the Grey Knights' fortress-monastery on Titan is known only to the Ordo Malleus. Titan itself is surrounded by the rings of Saturn and the other moons of the gas giant which are all highly-secret Inquisition-controlled worlds, including: Mimas, the prison and execution centre of the Ordo Malleus, Enceladus, the home of the most powerful Inquisitor Lords of the Ordo Malleus and other influential Inquisitors of that Ordo, and several other satellite worlds all dedicated to the secret task of confronting the corruption of Chaos across the galaxy.
Beneath the Grey Knights' fortress proper lies a cool, damp crypt. It is here that every Grey Knight wishes to finally reside, in the hallowed halls of the glorious dead. Almost every member of the chapter will have their body recovered and brought to this crypt beneath the large Temple of the Emperor. As a final tribute to those members of the Chapter that have given their lives in the defence of the Imperium, the names of the dead are carved ceremoniously into a great basalt wall in the heart of the fortress. Among these names are some of the Imperium's greatest heroes who died in the most horrific circumstances imaginable battling the Forces of Chaos. And like all other matters in regard to the Grey Knights, they will remain almost completely unknown to the rest of the Imperium because of the official policy of denying the existence of Chaos and its daemonic agents.
The fortress-monastery of the Grey Knights on Titan also contains the infamous Librarium Daemonica, the foremost repository of lore on the Warp, sorcery and daemonology in the Imperium of Man. The Librarium is a forbidding place, filled with tens of thousands of tomes, logic stacks and data crystals of diabolic lore the Ordo Malleus has accumulated over the millennia, all maintained by a corps of mnemonic Servitors whose rudimentary minds are routinely wiped to prevent even their basic intelligence from being twisted by the arcane knowledge of the Librarium. The Librarium was placed within the Grey Knights' fortress-monastery because even other Inquisitors fear to be corrupted by the forbidden knowledge kept within; only the Astartes of the Grey Knights have so far proven truly incorruptible.
- Grey Knights (Novel) by Ben Counter
- Codex: Daemonhunters (4rd Edition)
- Codex: Grey Knights (5th Edition)
- White Dwarf 260 (Australian Edition), "Index Astartes - Purge the Unclean"
- Warhammer 40,000: Dark Millennium (1994), p. 22
- The Inquisition