Alpha Legion - Post-Heresy: In the aftermath of the Horus Heresy, the Alpha Legion did not retreat to the Eye of Terror like the other Traitor Legions; instead the XXth Legion moved on into the galactic east, following new objectives of their own devising. As such, the Legion was not pursued into the Eye of Terror as so many of their fellow Traitors were, but became embroiled in a series of bitter confrontations with the Ultramarines, who themselves had been engaged in that region when Horus had assaulted Terra.On the world of Eskrador, the Alpha Legion was assaulted by Ultramarines forces. Alpharius was reportedly happy with such a development, as it allowed him to demonstrate the superiority of his flexible, multitudinous and unexpected military strategies over the notoriously precise, methodical and perhaps even tactically moribund Ultramarines.The Ultramarines' Primarch Roboute Guilliman would prove himself the better strategist when he accurately predicted that the Alpha Legion would believe they could foresee the tactics he would utilise in the coming battle. For perhaps the only time in his life, Guiliman acted contrary to his own firmly-held military doctrines, and it was Alpharius who walked into a trap. Accounts vary as to why the Ultramarines and the Alpha Legion fought one another at Eskrador.Some say Alpharius wanted to prove the superiority of his tactics, whilst Guilliman wanted revenge on one of the Traitor Legions for the mortal wounding of the primarchs' beloved Emperor, and so tracked down the traitorous Alpha Legion in the Eskrador System. Alpharius' Legion was the first to arrive and was able to choose their battleground and set what they believed to be the perfect trap for the upstart Ultramarines.With access to all the records of the tactics used by Guilliman during the Great Crusade, Alpharius used this information to take full advantage of the Ultramarines' standard operating procedures. At first the battle was a stalemate between the two evenly matched Legions, but Guilliman chose nightfall to do something unexpected, leading a large portion of his forces with no lines of support or supply deep into the mountains where they deployed by Thunderhawk, Drop Pod, and teleporter in the midst of the Alpha Legion.The Ultramarines quickly took advantage of the situation and soon had the Alpha Legion's command centre in disarray. Hard-pressed by the vengeful Loyalist force, which outnumbered them five to one, the Alpha Legion was unable to fall back up the mountain valley. They were hampered by the terrain and were forced to make a last stand at the head of the valley.Alpharius himself led a furious counterattack against the Ultramarines and was slain in single combat by Roboute Guilliman. However, once again, there is now some doubt as to whether this "Alpharius" was actually Omegon, the twin primarch who had survived the Horus Heresy, or just another Astartes of the Alpha Legion wearing his primarch's armour. This final deception would present the Imperium with an unexpected and very nasty surprise time and time again.Having burned the supposed Traitor primarch's body on a great pyre, Guilliman led his Legion against the remnants of the Alpha Legion on Eskrador, only to discover that far from collapsing, the XXth Legion was mounting a series of cunning and often devastating counterstrikes. The Alpha Legion responded not by breaking and fleeing as Guilliman had expected after the death of their primarch, but by turning on the pursuing Ultramarines detachment and harrying them so mercilessly that by the time they had returned to the main body of the Ultramarines force their casualties were almost total.After solar days of bitter fighting, Guiliman gave up hope of an honourable victory and departed Eskrador, ordering a massive orbital bombardment to finish the XXth Legion's survivors off. Some Imperial savants have claimed that the entire battle was some grand ploy unleashed by the Alpha Legion, though to what end none can say. Certainly, the Alpha Legion fought in the manner of the mythical beast that adorns their armour -- the hydra -- for each time one head was cut off, another two grew back to replace it.Following the Battle of Eskrador, the Alpha Legion fractured in order to hide from the Imperium. Small, autonomous warbands were left in Imperial space where they set up secret bases in asteroid fields, on Space Hulks and on barren, unpopulated worlds. These units launched frequent attacks against Imperial military targets that had already been weakened by the Heresy and even today these warbands still pose a threat to Imperial starships, settlements and garrisons.The Alpha Legion's warbands also coordinate the spread and actions of Chaos Cults throughout the galaxy in order to instigate massive planetary revolts against Imperial rule. These insurrections are often used to lure Imperial forces away from more strategic worlds the Alpha Legion proper wants to attack, paving the way for large-scale assaults of Chaos Space Marines from the Eye of Terror.Unlike the other Traitor Legions, most of the Alpha Legion does not reside in the Warp, but rather roams the galaxy as scattered warbands of warriors, each of which is trained to act independently of the others in pursuit of their greater cause. In this way the Alpha Legion was by and large the only Traitor Legion not to succumb to the mutations of Chaos, an outcome that may also have been dictated by their continued secret loyalty to the Emperor of Mankind.The Alpha Legion's role in spreading heretical Chaos Cults across the Imperium has earned them the loathing of the Inquisition, whose Ordo Malleus and Ordo Hereticus have devoted considerable resources to finding and destroying their secret bases. The Alpha Legion has been declared exterminated by the High Lords of Terra no less than three times, in the 31st Millennium, the 32nd Millennium and the 39th Millennium. These claims have always been disproved by the next Alpha Legion-inspired plot or rebellion that breaks out somewhere in the Imperium and proves that the hydra still has more heads to slay.