Navis Nobilite

The Navis Nobilite is an ancient organization predating even the creation of the Imperium of Man by several thousand years, and is comprised of a unique form of human mutants called Navigators who have the unique psychic ability to navigate spacecraft through long distances in the chaotic eddies of the Warp.

The Paternova
The great leader of the Navis Nobilite, who is chosen from among the most powerful Navigators of the existing Great Families. The Paternova rules from the Palace of the Navigators on Terra. His position is far more than just one of leadership, for he is able to somehow control, or amplify, the Warp sight of the other Navigators. Without him, Navigators would suffer a considerable reduction in their ability to navigate the Warp, with some losing the power altogether. Without the aid of a Navigator, Warp travel becomes far more unstable, if not outright dangerous over any more than few light years travel distance.

The Great Families
The Navis Nobilite consists of several noble Houses or Great Families, consisting of a large group of related Navigators who reside within a literal house on Terra. This house is generally a large fortress-mansion presided over by the Great Family's leader, a powerful Navigator called the House's Novator. There the Novator lives with his immediate family and retainers.

Status
The Navigator Houses hold a unique position within the Imperium; by ancient agreements concluded with the Emperor before the Horus Heresy, they are not answerable to the authority of the Imperium, but tend to toe the Imperial line because of the mutual benefits each side receives. Furthermore, members of the Navis Nobilite are compelled by ancient and binding oaths to serve with the Adeptus Mechanicus for a set duration in return for the tech-priests' services, serving both the Imperial Navy and the various Imperial Merchant Fleets that keep the wheels of the Imperium's commerce turning. However, this political autonomy does not protect the Navigators from the agents of the Inquisition. The Ordo Malleus has been assigned jurisdiction over the Navigators, to ensure the taint of Chaos is not able to take hold among these unusual psykers. Given the slightest reason, the Inquisition will ruthlessly purge any offending parties among the Great Families; goods and assets are seized, midnight raids on Navigator palaces are followed by arrests and a purging of those seen as tainted; their fate is to be burnt as heretics or locked away in Inquisition torture chambers. As such, the Navis Nobilite are all too willing to tackle the problem of heresy or corruption internally.