The Thramas Crusade was a campaign conducted by the traitorous Night Lords Legion during the opening years of the galaxy-wide insurrection known as the Horus Heresy in the early 31st Millennium. Following the Traitor victory during the Drop Site Massacre of Istvaan V, the Warmaster Horus Lupercal despatched the homicidal Primarch Konrad Curze and his psychotic VIIIth Legion on a campaign of genocide against the Imperial strongholds of Heroldar and Thramas in the Aegis Sub-sector of the Eastern Fringes located in the Ultima Segmentum, thus protecting Horus' flank and delaying the Dark Angels Legion from reinforcing the Loyalists. This bitterly contested campaign would drag on for nearly three standard years.
Following the victory of the Drop Site Massacre at Istvaan V, Horus called a meeting of the 8 Primarchs of the Traitor Legions (minus the participation of the Alpha Legion's Primarch Alpharius) aboard his flagship, the Vengeful Spirit. Five of the Primarchs met in person, including Horus, Fulgrim, Angron, Mortarion, and Lorgar. Three appeared through the use of hololithic emitters that transmitted their signals through the Warp, including Perturabo, Konrad Curze and Magnus the Red, who had only recently joined the Traitors after the Scouring of Prospero, when the broken remains of his Thousand Sons had been transported by Tzeentch into the Eye of Terror to the Planet of the Sorcerers. The conclave of Traitor Primarchs made ready their plans for the next step in their war against the Emperor. With the meeting complete each Legion went its way according to its assigned role.
The Night Haunter's fleet, augmented by the entirety of the Traitor Titan Legion of the Legio Ulricon, had already departed, bound for the planet of Tsagualsa, a remote world in the Eastern Fringe that lay shrouded in the shadow of a great asteroid belt. From there, the Night Lords' terror troops would begin a campaign of genocide against the Imperial strongholds of Heroldar and Thramas, star systems that, if not taken, would leave the flanks of the Warmaster's strike on Terra vulnerable to attack. The Thramas System was of particular importance, as it comprised a number of Mechanicus Forge Worlds whose loyalty was still to the Emperor. Before Horus' traitorous plans were revealed he had sent unwary Primarch Lion El'Jonson and the bulk of the Dark Angels Legion to the Eastern Fringe, to perish at the murderous hands of their treacherous kin.
Following two years of bitter fighting, and extensive losses on both sides, the Lion could barely scarce to give it countenance. In an attempt to sway his brother Lion El'Jonson to Horus' cause, the Night Haunter left a deep-void beacon in the patrol path of one of the Dark Angels' outrider vessels. The beacon was set to transmit coordinates in advance, so that the two Primarchs could meet and parley on the planet of Tsagualsa. Night Haunter wanted to break his former brother either mentally, physically or both to obtain his objectives. The Primarchs were accompanied by two warriors from their personal Honour Guards to the parley. Lion El' Jonson was accompanied by Paladin Corswain of the 9th Order and Master Alajos, while Konrad Curze was flanked by First Captain Jago Sevatarion and his Equerry, Captain Sheng. The meeting began amicably enough between the two as they conversed with relative civility. This amity lasted only until the Night Haunter slandered the Lion, and in return the Jonson struck his former brother. This melee further degenerated into an all-out brawl between the two sides. Kurze manages to gain the upper hand and strangled the life out of El'Jonson. Fortunately, Corswain ran his sword through the Night Haunter's back, thus saving his Primarch's life and rendering Kurze comatose. Eventually both Legions sent reinforcements in response to this incident. Each side dragged away their respective Primarchs from the scene of the combat. Both Primarchs survived this brutal confrontation and went on to continue the contest between their Legions for control of the Aegis Sub-sector.
When next they fought, the Dark Angels executed a meticulously planned ambush on the Night Lords' fleet while it was in transit across the sub-sector that saw the back of the Night Lords Legion broken and their Primarch mortally wounded after having faced his brother El'Jonson once again in mortal combat. Thanks to the skilled coordination and superb execution by the Lion, the entirety of the Legio Ulricon's fleet was annihilated, causing their doomed vessels to spill their deadly cargo of Titans into space, which caused devastating losses to the Night Lords fleet. This resulted in the loss of dozens of VIIIth Legion capital ships and approximately one-quarter of their Legion fleet to the Dark Angels' assault. Unfortunately, the remainder of the Night Lords fleet fled the Dark Angels' wrath, while the recently recovered Night Haunter, First Captain Sevatarion and the elite Night Lords Atramentar Terminators led a desperate boarding assault action upon the Dark Angels' flagship, the Invincible Reason. This resulted in the death of all but a dozen of the Atramentar and the capture of Sevatarion and the remaining survivors. Konrad Curze fled El'Jonson's wrath, evading the Dark Angels for months, stalking the shadows within the bowels of the mighty capital ship for months. Lurking and stalking the shadows, avoiding the Dark Angels search parties and Lion El'Jonson himself, eventually the Night Haunter effects his escape.
Although the Night Lords suffer a devastating defeat, and the complete loss of the Legio Ulricon at the hands of the Dark Angels, their overall mission of protecting Horus' flank was, more or less, considered a success. The three-year long conflict delayed the Dark Angels long enough that by the time they defeated the Night Lords, and arrived at the Battle of Terra nearly five years later, the conflict would already be over.
Although the Night Lords' role of protecting Horus's flank was ultimately in vain, since Horus was defeated by the Emperor, the delaying of the Dark Angels also had the added effect of distracting them from Luther's betrayal on the Dark Angels' home world of Caliban. Subsequently, this betrayal would result in the destruction of their homeworld and would forever after steer the course of the Ist Legion and its latter Successor Chapters in the capture of their wayward kin, known as the Fallen, to the present 41st Millennium.
The remnants of the Night Lords Legion eventually regrouped in the Eastern Fringe, and with the absence of a Loyalist Legion, the VIIIth Legion would conducted a massive campaign of genocide and terror against the Imperium across the Eastern Fringe of the galaxy, the likes of which has never been seen before, or since. The Legion betrays the growth of the increasing sense of self-destruction which drives its Legionaries, much as it drives their Primarch. The Night Haunter, near fatally-wounded twice, and distraught at the death of First Captain Sevatar, fled to his dark lair on the planet of Tsagualsa, becoming a mad, naked, hunched-backed monster, until his assassination at the hands of the Callidus Assassin M'Shen. With the death of their Primarch and their First Captain Sevatar, the Night Lords slowly broke up into smaller bands and join assorted Chaos Lords and their presence in the Eastern Fringe diminished.
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