The Paternova is the leader, and most powerful, of all the Navigators.
The Paternova lives in the Palace of the Navigators, in the centre of the Navigator's Quarter on holy Terra. From the moment he is installed, the Paternova never leaves this palace. The staff, soldiery and other retainers of the palace are all drawn from the Paternova's own House, and are replaced with each new Paternova. The chief among his servants is the Paternoval Envoy, who often becomes one of the High Lords of Terra, representing the Navis Nobilite on the Senatorum Imperialis. If anybody were to know the secrets of the Navigators' origins, it would be the Paternova.
The chief role of the Paternova is his ability to somehow control, or amplify, the ‘warp sense’ of the other Navigators. This is a direct result of the extreme mutations they suffer during their ascension from one of the the Heirs Apparent. For this reason the Paternova is sometimes described as the guiding father whose powers transcend the warp itself. The importance of this link is demonstrated during the rare interludes between the reign of a Paternova and his replacement. During these times, all Navigators other than the Heirs Apparent suffer a considerable reduction in their ability to navigate the Warp. Were this state of affairs continue for long, much of the Imperium would collapse into anarchy, as ships would be unable to quickly traverse the warp, with many being lost completely.
The Paternova can often live for a thousand years. When he does die, his successor is chosen from among the waiting Heirs Apparent, the most powerful Navigators of the Great Families. From the moment of his death, all the existing Heirs Apparent undergo dramatic change. They grow larger and stronger, and the mutations that characterise all Navigators become even more pronounced. They gain the ability to survive underwater, in poisonous environments and even in the hard vacuum of space. Their natural aggression is increased, and they are drawn into combat with each other. As each Heir Apparent is killed, those who survive change even more, until only one remains alive. It is this vastly changed and extremely powerful individual who becomes the new Paternova.
As soon as the new Paternova is installed, the Navigators' powers are restored, though not all are restored to the same degree. Those Navigators belonging to the same House as the Paternova find their abilities enhanced, as though their blood tie enabled the Paternova to transmit his powers more effectively. Navigators belonging to the House of the old Paternova lose this benefit, and many Navigators suddenly find their powers greatly diminished. The reasons for this are unknown.
During the Horus Heresy, the Paternova was so threatened by the Dark Glass and Golden Throne projects (as they threatened to render the Navigators obsolete) that he dispatched agents to destroy at least the former.