- "The Emperor of Mankind is the Light and the Way, and all His actions are for the benefit of mankind, which is His people. The Emperor is God and God is the Emperor, so it is taught in the Lectitio Divinitatus, and above all things, the Emperor will protect..."
- —Living Saint Euphrati Keeler
Euphrati Keeler was originally a Remembrancer during the final days of the Great Crusade aboard the Warmaster Horus' flagship Vengeful Spirit. Her experiences in the latter days of the Great Crusade transformed her from a normal young woman with no special abilities into a devoted believer in the divinity of the Emperor of Mankind, a faith so deep that it would prove to be a bane to daemons and other servants of Chaos. After the Horus Heresy began, Keeler would be recognised by others who shared her beliefs as a Living Saint, the Prophet of the Emperor. This reputation would see her later canonised as one of the first saints of the Imperial Cult and the Ecclesiarchy.
Euphrati Keeler was a young Remembrancer from Terra who was a part of the program initiated by the Emperor of Mankind to embed humanity's greatest chroniclers and artists among the Expeditionary Fleets of the Legiones Astartes during the final days of the Great Crusade to unify the human-settled galaxy. Their function was to chronicle all the glorious deeds of the Space Marine Legions and the Imperial Army in the course of the Crusade so that the future posterity of the Imperium of Man would know how humanity had come to dominate the galaxy. Keeler served as an imagist (photographer).
Her more famous images from this time include the rescue of Maloghurst from the surface of the world designated Sixty-Three-Nineteen, and Garviel Loken taking his Oath of Moment before the Battle of the Whisperhead Mountains, the final battle that completed the Imperial Compliance campaign for that world. She and other Remembrancers were allowed to travel to the surface of Sixty-Three-Nineteen during that final battle, though they were meant to go nowhere near the actual combat. On an impulse, Keeler's group of Remembrancers slipped away from their Imperial Army escort and entered the final rebel stronghold in the Whisperhead Mountains. While in the tunnels of the rebel outpost, Keeler was shaken by an encounter with the daemon calling itself Samus in the Whisperheads. The daemon possessed the body of Luna Wolves Sergeant Xavyer Jubal and proceeded to kill the entire group of twelve accompanying Luna Wolves Astartes except for Keeler and the Imperial Iterator Kyril Sindermann. Though the incident was covered-up by the Warmaster Horus, the terrifying experience may have later contributed to her eventual decision to join the Lectitio Divinitatus, a widespread cult across the Imperium that rejected the materialist doctrines of the Imperial Truth and worshipped the Emperor of Mankind as a deity, prefiguring the rise of the Imperial Cult.
Her growing devotion to the Emperor as a god in the wake of the incident in the Whisperhead Mountains became clear later when Kyril Sindermann accidentally summoned a daemon using a copy of the Book of Lorgar in the library of the Vengeful Spirit, Horus' flagship. Keeler stood before the creature with the symbol of the Aquila and banished it back into the Warp with the power of her faith. Following the banishment, she collapsed into unconsciousness for an extended period of time, entering what could only be described as a restorative coma. But news of her miraculous deed spread through the 63rd Expeditionary Fleet, leading the many Divinitatus members covertly present in the fleet to see her as "the Saint", the venerated Prophet of the Emperor. She became a target of Horus' assassins after his turn to the service of Chaos, including Maloghurst's enforcer Maggard. She awakened from her catatonia shortly before the Istvaan III Atrocity, and warned that something dark had grown within the confines of the Warmaster's Legion.
Keeler escaped the 63rd Expeditionary Fleet and Horus' slaughter of all the other Remembrancers present on the Vengeful Spirit with Mersadie Oliton and Kyril Sindermann aboard the Imperial frigate Eisenstein that was commandeered by the Loyalist Death Guard Battle Captain Nathaniel Garro. Keeler and the others had only escaped the Vengeful Spirit with the help of the Luna Wolves Captain Iacton Qruze, who she approached for help after witnessing the Traitors' bombardment of their own Loyalist brethren on the surface of Istvaan III. Keeler became an increasingly avid proponent of the Lectitio Divinitatus during the journey to Terra. Her faith in the Emperor would prove to be so absolute that it would provide psychic protection against the powers of daemons summoned from the Warp. After she arrived on Luna, she was taken into custody by the Sisters of Silence, who believed her to be a renegade psyker. She was interrogated by them within their fortress on Luna known as the Somnus Citadel.
As the Heresy progressed, Keeler gained great sway over the masses of the Imperium as she was increasingly identified simply as "the Saint." She began to spread the teachings of the Lectitio Divinitatus across the homeworld of Mankind, bringing millions of new followers into the faith. Horus ordered the Vindicare Assassin Eristede Kell to kill her and thus badly damage the morale of the Loyalist population of the Imperium and unleash the chaos of religious strife on Terra before his final assault on the Throneworld. Kell had originally been sent along with four of the other greatest Imperial Assassins to kill the Warmaster on the world of Dagonet, but the plan failed, and after several standard years of hiding aboard the Vengeful Spirit, Kell was eventually captured and turned to the service of Horus. The Warmaster returned Kell to Terra but his attempt to assassinate the Saint was ultimately foiled at the last moment by Nathaniel Garro, now one of Malcador the Sigillite's Knights-Errant. Afterwards, Keeler was taken under the Sigillite's personal protection, despite her repeated violations of the Imperial Truth.
Keeler's fate after the end of the Horus Heresy is currently unknown in Imperial records.
After her turn to faith in the Emperor as the God of Mankind, Euphrati Keeler began to manifest a number of supernatural abilities, including the power to banish daemons in realspace back to the Warp. By the time of the battle against Eristede Kell on Terra, Keeler's abilities had grown enormously, and now included the power to share precognitive visions of the future, spontaneously heal wounds, and stop the flow of time to facilitate communication with others. These abilities were not directly psychic in themselves, as Keeler was not known to be a psyker before her conversion, but were derived from her extraordinary faith in the Emperor's divinity. This gave her access to the power of the Warp in an unconventional manner like the Living Saints who would come after her in Imperial history.
During her time aboard the Vengeful Spirit before the start of the Horus Heresy, Keeler took several images of a comet passing near the world of El'Phanor, which was later named the Keeler Comet in Imperial astrocartographic databases in her honour. The comet was named for Saint Euphrati Keeler, which indicates that whatever Keeler's fate during the Heresy, she was eventually canonised as an Imperial Saint at a later time after the establishment of the Adeptus Ministorum and the Imperial Creed as the state religion of the Imperium of Man.
Euphrate's Warp is the name for an unknown spatial phenomenon in the Sabbat Worlds Sector of the Segmentum Pacificus. Despite the difference in spelling, it is assumed this feature of the sector was named for the saint.
- Horus Rising (Novel) by Dan Abnett
- False Gods (Novel) by Graham McNeill
- Galaxy in Flames (Novel) by Ben Counter
- Flight of the Eisenstein (Novel) by James Swallow
- Vengeful Spirit (Novel) by Graham McNeill
- The Sabbat Worlds Crusade (Background Book) by Dan Abnett, pg. 7
- Garro: Vow of Faith (Novella) by James Swallow