High Lords of Terra - The High Lords: Since the dark days of the Horus Heresy, the number of seats on the Senatorum Imperialis has largely remained the same, fluctuating during various points of crisis before eventually returning to its original number of 12.Each seat is filled by a leader from one of the most powerful adepta and other organisations of the Imperium. A complex web of tradition, skulduggery, promises of support, threats of retaliation and considerations of mutual interest binds them together and determines who holds office and who does not.In practice, some of the Imperium's adepta and institutions are so powerful and vital that it would be unthinkable for their leader to not be granted a seat amongst the High Lords of Terra. Naturally, over the long millennia, the unthinkable has happened many times over, however, and the existing High Lords often put in place an inordinate amount of measures to ensure that their seat is a permanent one -- that upon their deaths their position is automatically filled by the new head of their organisation.The following offices are almost invariably represented as High Lords because they form the cornerstones of the Imperium, the most important of its ancient institutions.Although the sources regarding the exact composition of the Senatorum Imperialis are varied, some institutions and organisations within the Imperium are so powerful that their leaders can be considered a de facto High Lord. The following nine offices are almost always represented as High Lords:The Master of the Adeptus AdministratumThe Representative of the InquisitionThe Ecclesiarch of the Adeptus MinistorumThe Fabricator-General of the Adeptus MechanicusThe Grand Provost Marshal of the Adeptus ArbitesThe Paternoval Envoy of the NavigatorsThe Master of the AstronomicanThe Grand Master of the Officio AssassinorumThe Master of the Adeptus Astra TelepathicaThese nine posts are virtually sacrosanct, and there are very few times in the history of the Imperium when their seats upon the High Lords of Terra became empty and were not filled with a successor from the same organisation.Note that a specific Inquisitor does not typically hold the position of Inquisitorial Representative on their own, but instead, the seat is retained for whichever individual is sent on behalf of the Inquisition during a meeting of the Senatorum. The eldest Grand Master of the Grey Knights is also occasionally present as the Inquisitorial Representative.Similarly, the place of the Paternoval Envoy is open to whoever might be the Envoy of the Paternova of the current ruling family of Navigators. The Paternova himself never leaves the Palace of Navigators, for it is forbidden for him to do so.To prevent a monopoly on power, the strongest Navigator houses usually agree to elect a Paternova from the weakest Navigator houses.If a strong house were to rise to power in the Senatorum Imperialis, that house would gain control of the Navigator's voice in the Imperium and thereby control all but the strongest Navigator families.The total number of High Lords is said to be twelve, leaving three non-permanent openings. These positions are most often filled from among the following powerful Imperial leaders:Lord Commander of the Segmentum SolarLord Commander Militant of the Astra MilitarumLord High Admiral of the Imperial NavyCardinal(s) of the Holy Synod of TerraAbbess Sanctorum of the Adepta SororitasCaptain-General of the Adeptus CustodesChancellor of the Estate ImperiumSpeaker for the Chartist Captains (representative of the Imperial merchant fleets and the Chartist Captains)Lord Constable of the SynopticonIt is an oddity that, throughout its history, very few members of the Adeptus Astartes have served among the High Lords of Terra -- given the importance of humanity's most elite fighting force and the fact that the first council was initiated by Roboute Guilliman, the primarch of the Ultramarines and Lord Commander of the Imperium.This seems to have been set up intentionally by Guilliman, who knew that at times of great need, Space Marine leaders would have no choice but to step in, but would otherwise remain outside Humanity's ruling structure.Some say the primarch's discouragement of Space Marines serving in the Senatorum Imperialis was based upon the Emperor's original Council of Terra -- which was separate from His War Council, and a ruling body that did not include any Astartes.Guilliman clearly believed, as his great work, the Codex Astartes points out, that it is the Space Marines' duty to serve Mankind, not to rule it, just as the Emperor Himself held.In its long existence, the Senatorum Imperialis has gone through many changes. The High Lords have been forced to give one of its seats over to a religious leader (the Ecclesiarch, who joined shortly after the Adeptus Ministorum was named the sole state religion of the Imperium in the early 32nd Millennium), wiped out to a man by assassination (on the orders of a slighted Grand Master of the Officio Assassinorum, an event known as "The Beheading"), and dissolved altogether by the ruling Ecclesiarch (during the civil war known as the Age of Apostasy).Many members have disappeared under suspicious circumstances and the Inquisition has been asked to investigate a number of times (although many have suggested that at least some missing High Lords of Terra have disappeared because of the Inquisition).Yet always, despite the many power struggles and strife, the High Lords of Terra have continued to interpret the Will of the Emperor and thereby rule the greatest empire in the galaxy.