This is the background to the XI Legion that I briefly mentioned in my story about the Amethyst Brothers II Legion I created. I thought I’d expand on them a little bit, and decided they would be “invisible” to psykers as some people have suggested one of the missing legions was. It's a bit of a weak background at some points, but as there isn't much real information on the two missing Primarchs, it's fine
By the time Horus fought the Emperor above Terra, the II and XI legions had both been removed from the material universe. The II Legion were trapped in transit in the warp, unable to assist their brother marines. The story of the XI Legion is a much darker tale, uncovering the secret hidden by the Emperor of the first ever legion to turn against his light.
Legion XI - Immortal Victors
Primarch - Antilaques
Homeworld - Gothen - Feudal World/unknown segmentum (Destroyed by order of the Emperor) Legion traits - Antilaques had an extremely small presence in the warp, which effectively made him a weak blank. This was passed on through his gene-seed to create a legion of marines who were almost unaffected by the touch of the warp. As such Librarians did not appear in this Legion, and marines of the Thousand Sons legion could not stand to be in the same room as the Immortal Victors, due to the painful anti-psychic resonance.
Colours - White, with checkered black and white on the shoulders.
The early years
Antilaques was found lying bawling at the top of his lungs in the centre of Gothen's main settlement by the Lord’s son, and his wife, who took him in as their child. As he began to grow older, they realised he was not the same as a normal human, excelling in all tasks. Due to his weak blank capabilities he often caused the hairs on the back of peoples necks to stand up when he was near, though it was not as uncomfortable as the effect of a full blank. When he was old enough, they sent him into the army, where he again excelled in all tasks, shocking everyone when, at a siege, with his cannon completely out of ammunition, he picked up the heavy weapon and used it to swat the enemy from the ramparts. This was followed by a whole reel of inhuman events that he did not boast about, merely calling it his duty. Eventually he gained the position of commander of the northern hemisphere. Leading a bloody swathe through his enemies, the entire population eventually became united under the banner of his father, who was now the Lord of the main settlement.
The Coming of the Emperor
The Emperor came not long after this event, the burning fire of his transports scaring many of the planets inhabitants as they flew like comets down towards the ground. On viewing menemerging from them, the people were reminded of myths of the first settlers on the planets, and their advanced technology, and realised these people had come to bring them forward to a new age. Antilaques was taken to the main ship, and told how he ended up on the planet and what the Emperor was doing. Those around him could see that it pained the Emperor to be so close to a blank, their two opposite natures conflicting with each other. The Emperor explained this and said that he was the most difficult Primarch so far, as he was utterly invisible to psykers and therefore harder to find. The entire population was put through rigorous tests to be inducted into the legion, and the Immortal Victors were sent on their crusade.
“Horus and his legion are not alone in his treachery, fully half of the legions will turn. The Word Bearers, Thousand Sons, Emperors Children, Death Guard, Alpha Legion, Night Lords, Iron Warriors and Immortal Victors shall turn.” - Primarch Amethis of the Amethyst Brothers. (From Glory to the Foresighted)
The Immortal Victors were frequently sent into areas of high warp activity by the Emperor, their near invulnerability to its effects gaining them an advantage. One such campaign however sent them against a force that stripped them of this advantage, wracking their bodies with chaotic energy. When they emerged from every battle, the Immortal Victors were getting weaker and weaker, the campaign slowly being won, through sheer brute force, but a third of the legion was destroyed. Antilaques felt betrayed by the Emperor as he had ordered them against these enemies, with no reinforcements arriving due to a clerical error, though he did not know this was the reason. Instead he thought the Emperor was trying to kill them all so that his blanks could not affect the Emperor and in a fit of madness would not listen to his reason. Vowing never to return to the Emperors side unless it was to kill him, Antilaques fled his campaign with the remaining men who became a piratical force, fighting against any warp-based enemy in their way, slowly removing the blank gene from their geneseed to produce a fully chaotic force. Furious at this, the Emperor ordered the destruction of his planet and struck their details from the records, having already lost the II Legion in warp transit a year before he was distraught that he had now also lost the XI. He proclaimed to the other Primarchs that xenos raiders had destroyed Antilaques planet, and the XI Legion were thought to be utterly annihilated, not wanting the true events to get out. He told them that if any returned he would bring their records back, though this would never occur.
The Horus Heresy
When the heresy occurred, the premonition of Amethis came true, and the Immortal Victors sought out Horus to pledge allegiance. As his force now only numbered half its original number, Antilaques joined his men to the Sons of Horus, the Imperial forces not stopping to notice that the colours of some of the enemy were those of the lost XI Legion. Thinking he would now get the chance of killing the Emperor, Antilaques told Horus of a plan he had devised to draw the Emperor out to his barge. Horus, seeing how this could lose him the respect of his legions, for not being the one to slay him, engaged in a battle with Antilaques and destroyed him. Ordering his legion to purge their ranks of any who would not follow him, Horus enacted the plan Antilaques had suggested.