Be ever vigilant against the threat of Chaos, for the Dark Ones always threaten to tear asunder all that we have accomplished... I shall tell you a tale of such a time, when the actions of two men almost brought to fruition the will of the Dark Gods... When the noble ideals of the emperors finest were tested, and all that they had accomplished seemed lost...
It was just before the time of the second Dark Age, when the world was seemingly in a golden era of peace and prosperity... The warriors of the Imperium were searching for more descendants of the Primarches; it was a time of fresh faces and new friends... But little did the Primarches know that amongst the righteous walked two souls twisted by the lure of chaos... One would be seduced by the bloodlust of carnage wrought by Khorne, the other would fall to the lure of greed, together they would bring the Adeptus Astaries to their knees...
We accepted them with open arms for they appeared to be honorable, and for a time the one known as Yitsel was, but the seeds planted by the dark gods were buried deep, so deep that even he did not see them... The other Dransor could not keep the tenements of the Emperor, and never really joined us... Dransor guided perhaps by the Dark Gods saw this seed in Yitsel, and made plans to exploit it... He hid his bloodlust from us for as long as he could, making friends with us, and especially with Yitsel. They hunted together all the while planting seeds of doubt and frustration within his heart, till finally one day, he could no longer control his bloodlust, and set it free killing an innocent traveler... This horrified Yitsel, to see the carnage of the blood god first hand... The Dark gods are not all-mindless killers however, and seeing an opportunity to gain another follower, the schemer known as Slannesh spoke through Dransor to Yitsel... "Look at them," he said, " See how easy it is to destroy them and take their possessions... They hold greater wealth than the creatures and beasts you have hunted until now... They are easy prey for the clever, and their riches are numerous..."
The Dark Ones showed Yitsel what could be attained by this lifestyle, in their vision, he saw all that he wanted in life money, fine weapons and armor, houses, and so on... His greed took control of him, and with it the Dark Gods took control of his destiny... Awash with Power and Indulgence, the two set out to find more innocents to slay and more possessions to steal... But the Dark Gods had not fully eradicated Yitsel's honor, and they knew it... It was after almost killing a noble ally of The Adeptus Astaries that Yitsel had seen what lay on this path for him... The Dark Gods seeing Yitsel's momentary laps into honor spoke to Dransor, telling him to speak to the Primarches for they should know the fear you command, and the blood you have shed in their names... Speaking to his ego drove Dransor to gloat about his deeds, and to make full mention to the Primarches of one of the Emperor's finests fall into darkness... This disturbed the Primarches for they knew that this betrayal deserved immediate action... But the Dark Gods had a plan, by not allowing Yitsel to think too much on his betrayal and by not allowing the Primarches to learn of his remorse, they had set in motion a plan for the downfall of the New Imperium... The Primarches not knowing the full story, and knowing what would happen if they delayed in action, the old memories of the Horus Heresy fresh in their minds did what they thought they must do... A show of force was necessary a show of force was called for...
After punishing Yitsel, the Dark Gods let it be known of Yitsel's remorse, this sent a ripple of guilt through the Primarches... The Dark Gods plan seemed to be rolling along smoothly... To further push the matter, the Dark Gods clouded the lines of communication between the Primarches Jamace and Marcalla... So clever was the god of deception Tzeenich that the Primarches themselves did not know of his influence... Meanwhile the third Primarch Dragco found evidence of the Dark Gods work in a distant part of the world known as the new lands... Knowing that Dragco was a psyker and could possibly see through their deceptions, they conspired to get him out of their way, the Dark Gods sent an army of their constructs to attack openly allies of his... Without Dragco to see through the mists they had woven over the communications of the two Primarches, the Dark Gods felt they had succeeded in tearing the Imperium apart...
It seemed to Jamace that Marcalla was not listening to him any longer, that he had assumed the place of the Emperor and sought to impose his will upon the warriors of the Imperium as well as himself... So he made the choice to leave the The Adeptus Astaries... When Jamace confronted Marcalla with this, He could not see why his friend was acting this way... He did not see the mists that wove between them, clouding their thoughts twisting their words... Try as he might, he could make Jamace understand that he did not want to exclude him, that he wasn't taking the place of the Emperor, but every word that came out of his mouth seemed to fall short of Jamace’s ears... He could not see why Jamace thought he was doing so... So with reluctance he agreed to Jamace's request to leave TAA... He sent word to Dragco of the conversation that he and Jamace had had, and the news of Jamace's inevitable departure... The Dark Gods delighted in this what seemed to them to be the final act... Little did they know that Dragco had returned from the New Lands and was on his way to the Primarches...
Dragco came to speak with Jamace, and upon his arrival, he noticed something hanging in the air of immaterial plane of the warp, like the buzzing of a swarm of insects, the mists rising off the moors in the early morning, something was clouding the air between the two Primarches... Seeking to break through this cloud he prayed to the Emperor for guidance, and was smiled upon... As he stared off to the warp, he could see no such clouds between himself and Jamace, nor could he see such clouds between himself and Marcalla... And the idea sparked within him... He would be the portal through which they would find understanding... as he spoke the mists began to abate, no longer driven by guilt and hopelessness they had no power... The Primarches began to talk and see each others side, they were understanding each other again... And thus the Imperium became united once again...
-Marcalla, Primarch Avenger, The Adeptus Astaries