- "There can be but one Emperor, one God, one Saviour, one Deliverer. Without Him, a billion billion souls are nought but fodder for the ever-thirsting evils of the Warp."
- — Ecclesiarch Theodacus V, Indroit to the Verses of Dusk
The Ecclesiarch is the nominal High Priest of the Imperial Cult and the chief administrator of the Adeptus Ministorum. Elected for life by the Holy Synod, a gathering of the most prominent Cardinals of the Imperium of Man, the Ecclesiarch's primary duties are to represent the Ecclesiarchy as one of the High Lords of Terra in the Senatorum Imperialis, to order the launch of Wars of Faith, and to monitor and maintain the devotion of the average Imperial citizen to the orthodox worship of the God-Emperor of Mankind.
Since the establishment of the Imperial Cult as the state religion of the Imperium in the 32nd Millennium, the Ecclesiarch has always held a position as one of the High Lords of Terra and has maintained a highly influential seat on the Senatorum Imperialis, at times acting as the Imperium's most politically powerful High Lord. The Ecclesiarch rules the Imperial Cult's galaxy-spanning priestly hierarchy from the massive, continent-sized Ecclesiarchical Palace on Terra, which is one of the most popular sites for pilgrimage in the whole Imperium.
On a related note, in many Low Gothic dialects, the term "Ecclesiarch" is used honourifically to refer to the most senior Ministorum priest of a given parish, as he or she is the local authority on matters of faith.
There have been close to 600 individuals who have borne the title of Ecclesiarch since the inception of the Imperial Cult as the Imperial state religion in the 32nd Millennium. The following short list contains the most (in)famous of those to occupy the Ecclesiarchal Throne on Terra:
- Veneris II - Ecclesiarch circa 200.M31, Veneris II was elevated as the first Ecclesiarch of the Imperial Cult to become a member of the Senatorum Imperialis. Died of old age.
- Erekart Veneris Sanguinan Mesring - A member of the powerful and wealthy merchant family of House Mesring who entered the Imperial Cult as a Priest, after he became Ecclesiarch in the middle of the 32nd Millennium, Erekart Veneris Sanguinan Mesring used his power to favour his family's commercial interests in the Senatorum Imperialis. This included voting against expanding the orbital shipyards in orbit of Uranus in the Sol System despite their safety in order to protect House Mesring's own shipyard holdings in the Tang Sector. Mesring was a close ally of the powerful Lord High Admiral Lansung who controlled the ruling faction of the High Lords of Terra at the start of the War of the Beast, alongside the Master of the Administratum Tobris Ekharth. These three sought to maintain their power over the Imperium by ignoring the growing threat of the Greenskins. Mesring was an elitist Imperial noble fop, widely known among Terra's elite for slapping subordinates with his obese hand. However this could not save him from the Grand Master of Assassins Drakan Vangorich, who infiltrated the Ecclesiarchal Palace and poisoned him. Vangorich told Mesring that he had only 3 solar days to live, and if he wanted the antidote he would declare a War of Faith against The Beast and force Lansung to redeploy his fleets against the Greenskins. After Mesring accomplished this, he somehow managed to remain alive, even though Vangorich had never intended to provide him with any way to survive. Following the appearance of an Ork Attack Moon over Terra and the fall of Lansung from grace, Mesring aligned with the newly ascendant Speaker for the Chartist Captains Juskina Tull. The Ecclesiarch supported the Speaker's disastrous Proletarian Crusade, providing vital vocal support and a religious blessing for the campaign. Mesring fell into a deep depression after the Crusade's failure and revealed that he had only acquired his antidote from Inquistorial Representative Wienand, but only enough to last for 25 solar days. The poisoning shattered Mesring's faith in the God-Emperor, and he secretly began praying to The Beast for his salvation. A physically frail and disheveled Mesring later abandoned Lord Commander of the Imperium Udin Macht Udo when he was overthrown by Chapter Master Koorland of the Imperial Fists and the Inquisition. A visibly unhealthy and unhinged Mesring later became the chief opposition to Koorland during his attempts to form the Deathwatch to deal with the Greenskin threat, as Mesring considered the action heresy. Even after Tobris Ekharth and the rest of the High Lords agreed to Koorland's proposal after the Attack Moon reactivated in orbit of Terra, Mesring still voted against the measure. When the Attack Moon shattered and blanketed Terra in debris, Mesring's Ecclesiarchal Palace was destroyed by the debris. Mesring survived and was found in the rubble days later, still screaming. As Vangorich's poison slowly killed him, Mesring's mind began to fail. Not even the Tears of the Emperor could cure him. Losing the last vestiges of his sanity the day before the poison was set to kill him, Mesring confronted Lord Commander of the Imperium Koorland and the rest of the High Lords, and denounced Koorland and Drakan Vangorich as Heretics. As he ranted, Mesring eventually declared his belief that the only hope for salvation lay in welcoming The Beast as the new god of humanity, and he openly praised the Ork Warlord as a deity before the High Lords. Koorland put the mas out of his raving misery and shot the Ecclesiarch in the head. His death was unopposed by the Ministorum and the rest of the Senatorum Imperialis because of his heresy, as even the Cardinals of his own Holy Synod condemned his heresy. Koorland proceeded to strip the Ecclesiarchy of its seat in the Senatorum Imperialis and revoked the Minsitorum's state-granted privileges. In the wake of The Beheading, the Ecclesiarchy regained its seat when Drakan Vangorich reappointed Ostulus as a member of the High Lords of Terra. The Adeptus Minisotrum would never again lose this permanent seat on the Senatorum Imperialis. Erekart was killed by the hand of Chapter Master Koorland of the Imperial Fists Chapter for heresy.
- Ostulus - Replaced Erekart Mesring as the Ecclesiarch in 546.M32. Ruled during the reign of Drakan Vangorich as the de facto master of the Imperium following The Beheading. Ostulus was the first Ecclesiarch whose seat among the High Lords of Terra was made permanent, and passed on to each of his successors. His cause of death is unknown.
- Benedin IV - Ecclesiarch during the 34th Millennium, Benedin IV announced in 200.M34 that the central seat of power of the Ecclesiarchy would be moved to Ophelia VII, distancing himself from the Senatorum Imperialis. His cause of death is unknown.
- Greigor XI - Ecclesiarch during the 34th Millennium, in 300.M34, Greigor XI announced that the Adeptus Ministorum's seat of power would return to Terra which increased Ecclesiarchial control of the Senatorum Imperialis. Many objected, but even after his death under mysterious circumstances, the planned move still transpired. His cause of death was poisoning.
- Alexis XXI - Ecclesiarch during the 35th Millennium, Alexis XXI was infamous for corrupting members of the Officio Assassinorum and employing Assassins to eliminate several recalcitrant governors, cementing the Ecclesiarchy's power over the rest of the Imperium. His cause of death is unknown.
- Paulis III - Ecclesiarch at the beginning of 36th Millennium, an utterly incompetent non-entity who was controlled and finally overthrown in a bloodless coup by the Master of the Administratum, Goge Vandire. Paulis III was executed for heresy by his successor.
- Goge Vandire - Ecclesiarch at the beginning of 36th Millennium, and also Master of the Administratum, he engineered the ascension of the degenerate Ecclesiarch Paulis III. Shortly after, Vandire topples Paulis and assumes the mantle of both High Lord of the Administratum and Ecclesiarch. Vandire's Reign of Blood begins. Almost 14 billion are slaughtered by the Divine Army during the Purge of Lastrati. The Daughters of the Emperor from San Leor are coopted into becoming Vandire's personal bodyguard, and are renamed the Brides of the Emperor. The Reign of Blood culminates in the Siege of the Ecclesiarchal Palace, at the height of which High Lord Vandire was executed by Alicia Dominica, the leader of the Brides of the Emperor, for heresy.
- Sebastian Thor - Ecclesiarch during the 36th Millennium, led the revolt against Goge Vandire and was promoted in his stead. Promulgated reforms including the Decree Passive and the creation of the Adepta Sororitas. Acclaimed as Saint and greatest Ecclesiarch ever. In 350.M36, Sebastian Thor returns to Terra for the last time, and passes away six solar months later at the age of 112. The entire Imperium mourns his passing, and he is declared a saint. Thor died of old age in office.
- Equitus XI - Successor of Sebastian Thor during the mid-36th Millennium. Reinstated the tradition of the Ecclesiarch taking a formal Ecclesiarchal name after the coronation rather than just using one's birth name. Finalised Sebastian Thor's reform and the organisation of the Adepta Sororitas, creating the convents and formalising the position of Abbess to lead the convents. He appointed Sister Palmiro of the Order of the Holy Word to the be the first Sororitas Abbess Sanctorum, the head of the Sisterhood, an office whose holder would prove to be an off-and-on again member of the Senatorum Imperialis over the next four-and-a-half millennia. Equitus XI died of old age in office.
- Alexis XXII - Ecclesiarch of the late 36th Millennium. It was Alexis XXII who split the existing Convent Sanctorum and Convent Prioris of the Adepta Sororitas into two convents each. His cause of death is unknown.
- Deacis VI - Ecclesiarch during the mid-38th Millennium. Deacis VI split the existing Adepta Sororitas Convents further, spreading the influence of the Sisterhood to the furthest reaches of the Imperium. The Order of the Bloody Rose was founded at the Convent Sanctorum in honour of Saint Mina during Deacis VI's reign. The Order of the Sacred Rose, founded in memory of Saint Arabella, the last of the six Sisters to enter the Throne Room during the Reign of Blood, is formed at the Convent Prioris. Deacis VI's cause of death is unknown.
- Inovian III - Ecclesiarch during the 39th Millennium. Canonised the Heroes of the Redemption Crusades as Imperial Saints, living incarnations of the Emperor's will. His cause of death is unknown.
- Umberto II - Ecclesiarch during the 39th Millennium. First Ecclesiarch since Goge Vandire to reaffirm the authority and power of the Adeptus Ministorum over the Imperium, he worked tirelessly to promulgate the Imperial Creed across the human-settled galaxy. Revered as an Imperial Saint and buried on the Cemetery World of Certus Minor.
- Decius XXIII - Current ruling Ecclesiarch in the late 41st Millennium, Decius XXIII is most famous for repeatedly clashing with the Inquisition.
|The High Lords of Terra (Senatorum Imperialis)|
|Permanent Members||Master of the Administratum • Inquisitorial Representative • Ecclesiarch • Fabricator-General • Grand Provost Marshal • Paternoval Envoy • Master of the Astronomican • Grand Master of Assassins • Master of the Adeptus Astra Telepathica|
|Rotating Members||Lord Commander of the Segmentum Solar • Lord Commander Militant • Lord High Admiral • Cardinal(s) of the Holy Synod of Terra • Abbess Sanctorum • Captain-General • Chancellor of the Estate Imperium • Speaker for the Chartist Captains|
|Ruling Member||Lord Commander of the Imperium|
- The Beast Must Die (Novel) by Gav Thorpe, Ch. 1
- The Beheading (Novel) by Guy Haley, Ch. 13
- Codex: Sisters of Battle (2nd Edition) pg. 6
- Codex: Witch Hunters (3rd Edition)
- Dark Heresy: Blood of Martyrs (RPG), pp. 8-15, 35-36, 41
- Echoes of the Long War (Novel) by David Guymer, Ch. 18
- I Am Slaughter (Novel) by Dan Abnett, Ch. 9
- Dark Heresy: Blood of Martyrs (RPG), pp. 8-15, 35-36, 41
- Predator, Prey (Novel) by Rob Sanders, Ch. 7
- The Emperor's Finest (Novel) by Sandy Mitchell
- The Hunt for Vulkan (Novel) by David Annandale, Epilogue
- The Last Son of Dorn (Novel) Chs. 2-3
- The Last Wall (Novel) by David Annandale, Chs. 5, 13
- Shadow of Ullanor (Novel) by Rob Sanders, Ch. 2
- Throneworld (Novel) by Guy Haley, Ch. 21
- Watchers in Death (Novel) by David Annandale, Ch. 4
- Warhammer 40,000 Rulebook (6th Edition), pg. 171