Lion El'Jonson was the Primarch of the I Legion of Space Marines, the Dark Angels. Following the events of the Horus Heresy, Jonson and his Crusading fleet returned to his homeworld of Caliban. Inexplicably, they were fired upon by the Dark Angel forces garrisoned there under the command of his once-trusted mentor and surrogate father, Luther, who had been entrusted with the custodianship of Caliban in the Lion's absence. Luther would eventually betray the Lion after allowing himself to be seduced by the offers of Chaos, rallying a good portion of the Dark Angels who had been left behind by their fellows to garrison the Legion's homeworld to his cause and attacking the Lion's fleet as he returned to Caliban. The titanic struggle between the two former friends resulted in the destruction of Caliban and the loss of the Dark Angels' Primarch, as well as the escape of Luther's allies who had sided with the Ruinous Powers. Known as the Fallen Angels amongst their former Battle-Brothers of the I Legion, it became the overriding goal of the Dark Angels and all of their Successor Chapters (collectively known as the Unforgiven) after the Second Founding to hunt down every one of the Fallen and get them to repent their betrayal of the Emperor and of the Lion. Perhaps one of the greatest secrets of the Imperium of Man, known only to the Emperor himself, is that the Lion is still alive and resting in stasis, buried deep within the Dark Angels' mobile fortress-monastery, The Rock. There he waits to be awakened to lead the Dark Angels in one final Crusade to save Mankind from all the enemies who threaten it with extinction.
During the event that isolated the infant Primarchs from the rest of the Imperium, Lion El'Jonson was cast to a hostile, feudal death world infested with monstrous, Chaos-warped Great Beasts that was named Caliban by its inhabitants. The humans of Caliban had regressed to a feudal state, yet still retained sufficient technology to produce armour similar in appearance, if not quality, to Imperial Power Armour and firearms similar to Bolt Pistols. Caliban was kept relatively safe from the Great Beasts by the Knightly Orders such as the Order and the Knights of Lupus.
The Lion was discovered as a feral child by the Knights of the Order, including the greatest man of the age, Sar Luther. Luther then named the boy Lion El'Jonson (meaning "Lion, Son of the Forest" in the Calibanite dialect of Low Gothic). In a very short time after this, the Lion replaced Luther as the greatest man on Caliban and became the Grandmaster of the Order. The Lion killed a great many of the death world's Great Beasts, including one of only two Calibanite Lions on the planet, the other being slain by the psyker and Supplicant of the Order Zahariel El'Zurias with the aid of the latent psychic ability later called terror sight that allowed him to slow down the perception of time enough to find an opening in the animal's defences.
During his career as a Knight of the Order, the Lion led a planet-wide crusade of all the Knightly Orders (save for the conservative Knights of Lupus) against the Calibanite beasts. If not for Luther, this crusade could not have occurred, as his influence was required to persuade the other Orders to participate. During the course of this crusade, both the beasts and the Knights of Lupus were exterminated. It was on the ceremonial last hunt of the beasts that the forces of the Imperium's Great Crusade would finally arrive on Caliban and reunite the Space Marines of the Dark Angels Legion (though they did not yet possess that name) with their gene-father.
Arrival of the Emperor
Eventually a unit of the Emperor of Mankind's forwards scouts from the I Legion of Space Marines arrived at Caliban and identified the Lion as one of the Emperor's missing sons, the Primarchs. Jonson was immediately given command of the I Space Marine Legion when the Emperor realised he had not only found one of his lost sons, but the genetic father of the Astartes who had landed on Caliban. Luther and the other members of the Order who passed the Legiones Astartes' trials were transformed into I Legion warriors, either as fully-fledged Astartes if they were young enough to undergo the implantation of the gene-seed organs, or through genetic manipulation to increase their physical abilities if they they were too old for the process, like Luther. After the new Astartes were ready, Jonson publicly re-named the First Legion the Dark Angels after an old Calibanite myth. Luther, too old to be a Space Marine, was the first to be genetically modified and became Jonson's second in command, as he had been during the Calibanite crusade against the great beasts. Jonson then left with the Emperor and the newly re-named Dark Angels to continue the Great Crusade.
The Lion was granted command of the 4th Expeditionary Fleet of the Great Crusade in orbit of the planet Sarosh. The Saroshi had recently expressed their interest in becoming part of the Imperium, and the Imperials were eager to allow them in, believing that these people seemed to possess the same secular beliefs as they did in the Imperial Truth. But the Saroshi secretly worshipped Chaotic entities in the Warp they called the Melachim ("kings" in ancient Hebrew) who may have been the Ruinous Powers or their lesser daemonic servants. They saw the atheistic stance of the Emperor's Imperial Truth as nothing less than a philosophy of pure evil since it would deny the very existence of their gods. The Lord High Exacter, the leader of the Saroshi bureaucracy, denounced El'Jonson and the Emperor to their faces aboard the Dark Angels' flagship. El'Jonson responded by impaling the Lion Sword through the fanatical Saroshi leader's body. However, unknown to the Dark Angels the Saroshi had also brought a nuclear device aboard their shuttle, intending to assassinate the fleet's entire command structure, including Jonson; however, Luther and a junior Librarian named Zahariel managed to eject the shuttle into space, causing only minor damage to the flagship. After this incident, Luther, Zahariel and two hundred other Dark Angels were sent back to Caliban in disgrace for allowing an enemy to get a nuclear device aboard the Primarch's flagship to oversee the recruitment of new Space Marines into the Legion from the Calibanite population.
As the years passed, news of Jonson's victories kept coming back to Caliban. The jealously which Luther had first felt on Jonson's appointment as Supreme Master of the Order grew with every report and the position Jonson had given Luther was not one suited to his ambitions. He slowly changed from an honourable knight to a man full of jealousy and hatred towards Jonson because he felt he had lost out on fame and glory. Additionally, new reports indicate that Luther discovered a book of Chaos lore on Caliban that gradually caused him to turn from the path of righteousness until he was consumed by the temptations of the Ruinous Powers and was transformed into a Chaos Champion.
The Lion and the Wolf
At some point during the Great Crusade, the Dark Angels and the Space Wolves Legions were assaulting the planet Dulan that had not given in to the Imperium's demands to become a compliant world. The leader of the rebels had insulted Leman Russ by naming him 'The Emperor's Lapdog'. Russ and his Space Wolves planned to assault rebel leader's stronghold for this blemish on their honor. While they were busy planning, the Dark Angels took the initiative and brought the fight to the capital instead and the Lion himself killed their leader. Russ found the Lion with the dead leader at his feet and immediately attacked his brother Primarch. They fought for a full day and a night, the combat ending only when the Lion threw Russ through a table. When Russ got up he started laughing at the foolishness of their quarrel. The Lion, incensed that his brother appeared to be mocking him, hit him square in the jaw, knocking Russ out cold. Russ awakened many hours later to find that Lion El'Jonson and his Dark Angels had already left the planet. Honour Duels are still fought between members of the Space Wolves and the Dark Angels to this day over this incident, which sometimes results in fatalities.
Return to Caliban
Jonson, wracked with grief over the inability of his Dark Angels to reach Terra in time to prevent the fall of the Emperor during the Siege of Terra at the end of the Horus Heresy, returned to Caliban to reinforce his Dark Angels and recover from the shock of the Heresy. When the starships arrived in Calibanite orbit, they were fired upon by a savage salvo of defensive fire from the surface. The fleet pulled back and Jonson tried to find out what was happening. He learned from a merchant ship that Luther had poisoned the minds of the Space Marine garrison on the world and taken control. It could only be seen by Jonson as the taint of Chaos. Jonson's fury was let loose and the planet suffered. He ordered a systematic orbital bombardment of the planet, to rid the world of Chaos for all time.
The planet burned and its defences were whittled down to nothing. Jonson led his forces personally against the defenders who had taken refuge in the Order's Fortress-Monastery. Jonson found Luther and saw him to be completely corrupted by Chaos, almost nothing of his old friend had survived. Luther, now a Chaos Champion, had been elevated to a strength equal to that of Jonson by the Chaos Gods and the two met in a combat the likes of which would not be seen again. They levelled the monastery around them but the planet was also taking a heavy toll. The bombardment began to crack the surface of the planet, the Dark Angels in orbit unable to see the damage they were doing.
The Final Battle
The battle between Luther and Jonson was titanic, but ended with a psychic attack that mortally wounded Jonson. Luther then realised what he had done, as if a veil of deceit had been lifted from in front of his eyes. He fell to the floor, unwilling to fight any more, but it was too late for Jonson. The enraged Ruinous Powers of Chaos realised they had lost again, and sent a massive Warp storm to wrack the surface of the planet. It then broke apart under the strain, destroyed all but for the monastery of the Order which had been protected by potent defensive force-fields. When the Dark Angels descended to what remained of Caliban, little more than an asteroid upon which stood the Order's fortress-monastery, they searched the ruins and found Luther mumbling that Jonson had been taken by the Watchers in the Dark and would return one day and forgive Luther for his sins. The Dark Angels could not find any trace of their Primarch. The rest of the Dark Angels who had been converted by Luther to the worship of Chaos were sucked into the Warp and scattered across the galaxy. From that time forward they were named the Fallen Angels or simply the Fallen.
The Fate of the Lion
During his duel with Luther on Caliban, Lion El'Jonson suffered a severe psychic blow which left him mortally wounded. He was then pulled into the Warp. Luther was taken prisoner by the Dark Angels and placed in a stasis cell deep within the bowels of the Rock (the remains of the Order's mightiest fortress-monastery and all that was left of their world Caliban), to contemplate his crimes against their Primarch. Jonson, whom was spirited away during the destruction of Caliban, was also taken into the deep, unreachable chamber within the Rock and placed into stasis to keep him alive. This is a secret known only to the Emperor of Mankind himself. Some say the Lion will eventually be awakened for one final crusade intended to lead the Dark Angels to their greatest victory for Mankind and finally bring justice and redemption to the remaining Fallen Angels.
- Lion Helm - The Lion Helm is a sacred object of the Dark Angels Space Marine Chapter. It is said to have been worn by Primarch Lion El'Jonson and takes the form of a winged Mark VII Space Marine Power Armour helmet. The helm is carried by a Watcher in the Dark. Built into the helmet is a protective force field which can be activated even when the helm is not being worn. The Lion Helmet is currently worn by Supreme Grand Master Azrael.
- Lion Sword - The Lion Sword is the great sword of the Primarch of the Dark Angels, Lion El'Jonson. The sword was broken in antiquity and lost. It is now rumoured to be carried by the mysterious Fallen Angel Cypher who seeks to reforge it and present it to the Emperor of Mankind, obtaining absolution and forgiveness for all of the Fallen who wish it.
- Citadel Journal 47, "Angels of Death", pp. 21–25
- Citadel Journal 37, "Tacticus Dark Angels", pp. 78–85
- Codex: Angels of Death (2nd Edition)
- Codex: Chaos Space Marines (3rd Edition, 1st Codex)
- Codex: Dark Angels (4th Edition)
- Codex: Dark Angels (3rd Edition)
- Codex: Space Marines (5th Edition)
- Codex: Space Marines (4th Edition)
- Codex: Ultramarines (2nd Edition)
- Deathwatch: Core Rulebook (RPG), pp. 44–46, 197
- Deathwatch: Rites of Battle (RPG), p. 236
- Deathwatch: First Founding (RPG), pp. 46–53
- Deathwing: Rules & Mission (1st Edition)
- Hammer & Bolter 17 & 18, "The Lion" (Novella) Parts 1 and 2 by Gav Thorpe
- Horus Heresy: Collected Visions
- Horus Heresy Vol. 1: Visions of War, pp. 13, 273, 278-279
- Index Astartes I, "The Unforgiven," pp. 4, 13, 18-23
- Index Astartes II, "For the Emperor!: Space Marine Chaplains," pp. 19, 56, 58-59
- Warhammer 40,000 Rulebook (6th Edition)
- Descent of Angels (Novel) by Mitchel Scalon
- Fallen Angels (Novel) by Mike Lee
- Age of Darkness (Anthology) edited by Christian Dunn, 'Savage Weapons' by Aaron Dembski-Bowden
- Angels of Darkness (Novel) by Gav Thorpe