The Trisagion was a part of a triumvirate of unique Imperial Abyss-class Battleships of special configuration, created and built in the early 31st Millennium. This vessel was constructed in secret during the latter years of the Great Crusade by the Renegade Dark Mechanicum faction loyal to Kelbor-Hal, the Fabricator-General of Mars' Mechanicum. This vessel was constructed for the Word Bearers Space Marine Legion, who were secretly ordered by the rebellious Warmaster Horus to bring their unfettered wrath down upon their hated rivals, the Ultramarines Legion. Following the destruction of his former flagship, the Fidelitas Lex, at the hands of an Ultramarines' retribution fleet during the Purge of Nuceria in the early days o the Horus Heresy, the Word Bearers' Primarch Lorgar took the Trisagion as his new flagship.
During the opening days of the Horus Heresy, Primarch Lorgar had ordered his two most trusted advisors, First Chaplain Erebus and the Dark Apostle Kor Phaeron, to unleash their unfettered wrath against the Realm of Ultramar. This was done in retaliation for the humilation the XVIIth Legion had been forced to endure by being forced to kneel in disgrace before the Emperor and Roboute Guilliman and his Ultramarines on the world of Khur at the Emperor's orders during the Great Crusade. The purpose of the Word Bearers' invasion of Ultramar in the Eastern Fringe of the galaxy was to tie down the XIIIth Legion, which administered the region as its Imperial fief, and prevent the Ultramarines from reinforcing their fellow Loyalists as the Traitor Legions marched relentlessly on Terra itself. To this end, Lorgar commissioned the Fabricator-General of Mars, Kelbor-Hal, in the construction of a mighty vessel of unique design, built on a scale never before seen by man. This gargantuan warship, the largest ever built by the Imperium, was christened by the Word Bearers with the name Furious Abyss. The Furious Abyss was to be manned by one thousand Word Bearers Astartes. They were led by Fleet-Captain Zadkiel, a devout and zealous follower of the Word of Lorgar. He was charged by the Dark Apostle Kor Phaeron to lead the assault upon the Ultramarines homeworld of Macragge, where they would strike the first blow for the Word Bearers against the hated Imperium of Man. But ultimately, Zadkiel failed in achieving his objective when the Furious Abyss was boarded by a small ad hoc force of Loyalist Astartes who had learned of the Word Bearers' role in Horus' rebellion and who proceeded to sabotage the massive vessel and destroy it before its array of formidable weaponry could be brought to bear against the worlds of Ultramar.
In the meantime, the Word Bearers' invasion of Ultramar proceeded to achieve a monumental victory at the Battle of Calth. The Ultramarines Legion was badly crippled by the Word Bearers' assault at Calth and no longer presented a viable threat to Horus' plan to drive on Terra. Erebus had managed to complete his blasphemous ritual on Calth's surface, which summoned the beginnings of the sorcerous Ruinstorm to the galaxy's Eastern Fringe -- a monstrous Warp Storm larger and more destructive than anything space-faring humanity had witnessed since the days of the Age of Strife. Simultaneously, with the Word Bearers' assault on Calth, Lorgar and the more reliable Word Bearers under his command launched a second offensive, a joint Shadow Crusade with his brother Angron and his World Eaters Legion into the rest of the Realm of Ultramar. They would go on to lay waste to the Five Hundred Worlds with reckless abandon, slaughtering twenty-six worlds in rapid succession. This was to ensure the success of the sorcerous Ruinstorm, which would ultimately split the void asunder, dividing the galaxy in two and rendering vast tracts of the Imperium impassable for centuries, effectively cutting Ultramar off from the rest of the Imperium.
Assault on Armatura
During one of their early campaigns, the joint Traitor fleet was to assault the War World of Armatura, a vitally important planet that fed the Ultramarines Legion with recruits and munitions. Its close-orbit played home to immense Imperial shipyards. Orbital bastions of linked gantries and docking maws drifted above the placid world. Above and beyond the shipyard was the first concentric ring of void defences. Here, weaponised satellites and fire platforms bristled with turrets, alongside independent landing decks for fighter craft in lockdown. Beyond those, the true defences began. These were literal castles in the sky: great fortress-stations with their own racks of fighters and entire battlements given over to plasma batteries, laser broadsides and ship-killing Lance arrays. In highest orbit, the outer sphere of satellites was a three-dimensional spread of solar panels, clockwork engines and slaved Servitor brains all connected to vast long-range weapons arrays. Amidst that outermost defence sphere waited the Evocati fleet. While the Legion mustered at Calth, the XIIIth Legion’s War World could never be left undefended. The Evocati was comprised of several thousand Ultramarines drawn from a dozen Chapters of the Legion, awarded the highest honour of all: overseeing the operations of Armatura and the training of new recruits, commanding an Imperial fleet to rival any other.
It appeared that Lorgar's plans to assault Armatura were for naught, for to attack the War World the Word Bearers would need a vessel to rival anything humanity had ever wrought. The Word Bearers had possessed such a vessel once -- the Furious Abyss. But it had been destroyed days earlier, close to the same moment Kor Phaeron's expeditionary force had struck Calth. Its corpse was probably still a shadow in the skies of Macragge, a monument to the Word Bearers' failure. Lorgar had told Zadkiel he was foolish to attack Macragge, but the Fleet-Captain was so keen to bathe in glory, for all he ever heard were the whispers begging for revenge for the humiliation of the Word Bearers on Khur. So the Aurelian had indulged him. But Lorgar had been underestimated, for he had planned for just such an eventuality. He had been planning the events that led up to the Horus Heresy for nearly half a Terran century. Lorgar's foresight became apparent when a vast trident of dark metal emerged from Warpspace near Armatura, a great warship whose shape was immediately familiar to the Word Bearers fleet approaching Armatura.
The starship that emerged into reality was a reflection of the slain colossus once called the Furious Abyss. A veritable city of monasteries and cathedrals rose from its back with the reverence of clawed hands sculpted to clutch at the stars. Where most Imperial Battleships were spears of crenellated intent and iron-ridged might, this was a fortress in space, borne on the back of a great trident. The central tine served as the vessel’s core: dense at the stern, encrusted with massive engines and tapering towards the prow, where it formed a pointed ram the size of lesser vessels. The trident’s adjacent tines formed smaller blade-wings, each one barnacled with laser broadsides and Macrocannon batteries. If one were to clad the concept of spite in iron and set it sailing amongst the stars, it might approach the image of what burst back into the universe in that moment. It was, in every way, the Furious Abyss reborn. This mighty vessel was the Blessed Lady. This colossus was named for the Word Bearers' former Confessor, Cyrene Valantion, the Confessor of the Word, and the lone survivor of the destruction of the Perfect City of Monarchia at the hands of the Ultramarines on the world of Khur. The Blessed Lady easily eclipsed the Gloriana-class Battleships used as flagships by most of the other Space Marine Legions. But Lorgar's final secret was yet to be revealed. He had not had only two of these mighty vessels built in the Mechanicum shipyards orbiting Jupiter. As a second Warp-slice ripped across the stars near Armatura, another colossus was revealed. This was the Blessed-Lady's twin sister-ship, the Trisagion. The pair of Dreadnoughts rivaled even the Imperial Fists' Primarch Rogal Dorn's precious Phalanx in size and firepower. Lorgar had secretly had three of these mighty vessels built for the service of the Word Bearers.
The Blessed Lady and her twin sister, the Trisagion, made a mockery of Armatura's orbital arrays, dismantling one of the best-defended worlds in the Imperium with barrage after barrage from their howling, flashing weapon decks. The ships’ size and scale rendered all countermeasures obsolete. For the first hour, nothing could punch through their Void Shields. Nothing even managed to scrape their skin. It took the combined firepower of a battle-station, two orbital defence platforms and a suicidal ramming from an Imperial warship to finally penetrate the Blessed Lady's shields. She sailed on, oblivious to the thousands dying within one of the flaming monasteries on her back, for their agonies made no difference at all to a crew composed of half a million men and women, all singing the praises of Logar and the Chaos Gods. The Word Bearers mighty Battleships made a mockery of the Ultramarines' defences and helped crush the Evocati fleet and win the day at Armatura for the Traitors.
Purging of Nuceria
During this campaign of destruction, Lorgar had come to realise that over the course of their Shadow Crusade, Angron's temperament and mental stability had steadily grown worse. The cortical implants known as the Butcher's Nails were killing him faster than Lorgar had originally imagined, faster than anyone realised. The rate of degeneration had accelerated very quickly in the months after the Battle of Calth. The implants had never been designed for the peculiar genetics of a Primarch's brain. Angron's physiology was trying to heal the damage produced by the implants as the Nails bit deeper. To save his life, Lorgar convinced the Lord of the World Eaters to go back to his homeworld of Nuceria, which lay near the Realm of Ultramar in the Ultima Segmentum. The overlords of the gladiatorial games on that world who had first hammered the foul device into Angron's skull would know more of the implant's function than the Traitor Legion's savants and the Dark Mechanicum. The two Primarchs would learn all that was known about the Nucerians' insidious cortical implant technology, and then they would burn that loathsome world until its surface was nothing but glass. Angron would finally take the vengeance he pretended to no longer desire. Whether Angron fought him, hated him or trusted him mattered little to Lorgar, who intended to drag Angron into the immortality that he deserved from the Dark Gods, whether he wanted it or not.
Twenty-seven days after the Conqueror and the Fidelitas Lex left Armatura in ashes, they broke from the Warp at the edge of Nuceria’s star system. The Trisagion was waiting for them. Once on Nuceria, Angron paid his respects to his fallen brothers and sisters amongst the Nucerian gladiators he had once fought beside, whose bones now lay exposed to the elements on the Desh'elika Ridge where they had died. The painful memories of that day, long ago, were too much for the Primarch to bare. After paying a visit to the city-state of Desh'ea to see who ruled the Nucerian city-state that had once claimed to own him, he became enraged when he was told the tale of how he had fled at the Battle of Desh'elika Ridge, and the subsequent massacre of the rebel army in the mountains. The rebels had died to a man in his absence. Enraged by the lies that had been told about him over the last century, Angron ordered his Legion to kill everyone in the city. Then they were to kill everyone on the planet.
As the World Eaters and Word Bearers lay waste to Angron's homeworld, the Traitors' fleet sat patiently in orbit, awaiting the completion of the murder of an entire world. Without warning, Roboute Guilliman's Ultramarines retribution fleet, which had been tracking the rest of the Word Bearers Legion in the wake of the Battle of Calth, finally caught up to the Traitors upon Angron's homeworld. The XIIIth Legion warship Courage Above All, Guilliman's temporary flagship, broke Warp at the system’s edge, at the head of a large void armada consisting of 41 vessels. The Ultramarines armada looked wounded, cobbled together from separate fleets. It was not a dedicated interdiction war-fleet, but clearly a ragtag strike force, a lance thrust to the enemy’s heart. Guilliman himself had done the best he could with limited resources. The XIIIth Legion's Cruisers and Battleships ran abeam of the enemy fleet for repeated exchange of broadsides, offering targets too big and powerful to ignore, while the rest of the Ultramarines fleet used calculated Lance strikes from safer range. The armada then divided its assault potential, doing its utmost to destroy Lorgar's flagship Fidelitas Lex, and attempted to take the World Eaters' flagship Conqueror in a boarding action.
Meanwhile, the Trisagion held its own despite the number of enemy vessels arrayed against the Word Bearers' fleet. The great Abyss-class Battleship was like a fleet unto itself. However, Lorgar's flagship, the Fidelitas Lex, was already a ruin, its armour pitted and cracked, its Void Shields a memory. The cathedrals and spinal fortresses barnacling along its back were gone, laid waste by the Ultramarines' incendiary rage. The XIIIth Legion's armada attacked in strafing runs and protracted exchanges of broadsides, trading fire with the superior warship and accepting their own casualties as the cost of bleeding the bigger vessel dry. Each assault left the Lex weaker, firing fewer turrets and cannons, taking punishment on its increasingly fragile armour. But she fought on. Crawling with smaller ships, the Lex lashed back with its remaining Macro-cannons, rolling in the light of its own burning hull. Guilliman guided the battle from the command deck of Courage Above All, and had decided that the Lex would die first, killed in the death of a thousand cuts and swept from the game board, while the Conqueror would be boarded and killed from within. In the course of the battle in Nucerian orbit, the Conqueror could not rise to its sister-ship’s defence. Both Traitor Legion flagships fought alone, starved of support and suffering the endless attacks of the XIII Legion’s ragged armada. Salvation Pods streamed from the Lex’s sides and underbelly, along with heavier Mechanicum craft and bulk landers. With the Legionaries of the Word Bearers already on the surface, the ship’s human population fled in the vessel’s final minutes. And still the great vessel fought -- rolling, turning, raging. But the Lex's destruction was inevitable, as the flaming wreckage of the once-proud flagship crashed to the planet's oceans below.
With the defeat of the Ultramarines and their Primarch on the surface of Nuceria at the hands of Lorgar and Angron, who had ascended to become a Daemon Prince of Khorne as a result of Lorgar's machinations, the Ultramarines retribution fleet recovered its troops and then withdrew from the system to lick its wounds. Following the completion of the Purge of Nuceria, Lorgar took the Trisagion as his new flagship. The ultimate fate of the Trisagion following the void battle at Nuceria is unknown in the fragmented Imperial records currently available from this time.
Likes its lost sister-ship the Furious Abyss, the Trisagion possessed a formidable array of weaponry, with hundreds of laser batteries that ran the length of both of its sides. It also possessed an experimental weapon: a Plasma Lance embedded in its prow, developed as a direct fire, close-range weapon for ship-to-ship combat, which was able to fire at point-blank ranges. The Trisagion could also deploy psionic mines when in transit through the Warp, to collapse stable Warp routes behind it when being followed by enemy vessels.
- Betrayer (Novel) by Aaron Dembski-Bowden