"No weapon in the arsenal of the Imperium or the Traitor equals the Titan on the battlefield, and a Legion of such war machines can bring any world to its knees. In truth a Titan has only three enemies: folly, hubris and another of its own kind."
— Grand Master Volkus, Ordo Sinister, Divisio Militaris
The Collegia Titanica is the division of the ancient Mechanicum and the current Adeptus Mechanicus that operates and oversees the Titans, the colossal Imperial war machines that are the most powerful engines of war in the Imperium of Man. The Collegia is also more rarely known as the Adeptus Titanicus (a contraction of "Adeptus Mechanicus Collegia Titanica") and as the Legio Titanicus in ancient records dating back to the Great Crusade and the Horus Heresy. Born of the time during the Age of Strife when the first temples to the Omnissiah were being raised on Mars, the Titans are the personification of the military might available to the Emperor of Mankind.
Bristling with massive cannons and missile launchers capable of wreaking terrible destruction upon an enemy, they dominate the battlefields of the galaxy and are a testimony to the consummate skills of the Tech-priests of the Cult Mechanicus. Every Titan is part of a larger unit called a Titan Legion. Each Titan Legion is based on a Mechanicus Forge World and remains under the direct control of the Adeptus Mechanicus, who jealously guard these mighty war machines and have the power to sanction which war zones they will commit their forces to.
It is this power that gives the rulers of the Adeptus Mechanicus much of their influence when it comes to determining when the armies of the Imperium will fight. It is a power which is coveted by other factions on Terra -- especially the Priests of the Ecclesiarchy, who would dearly love the reliable support of Titans for their Wars of Faith. The Titan Legions of the Adeptus Mechanicus are amongst the most powerful military entities within the Imperium of Man. Ancient and implacable, Titans are colossal engines of war, massive robotic combat walkers the size of multi-story buildings rightly known as "god-machines" or "god-engines" to the Tech-priests, who revere them as the physical embodiments of the Machine God.
Even the smallest class of Titan is mighty enough to destroy an entire tank squadron in a span of seconds or level a city block. Each Titan Legion is its own ancient warrior order inextricably linked to the Forge World (or worlds) on which it is based. The Titan Legions are fierce and proud, each with its own historic alliances and rivalries, and its own unique character that makes it somewhat similar to its counterparts amongst the Chapters of the Adeptus Astartes or the houses of the Imperial Knights.