The Emperor's Sickles were a chapter originally founded to help safeguard the eastern fringe of the galaxy. After a particularly brutal campaign in the galactic south, The Emperor's Sickles swore binding oaths with three other chapters; the Ashen Suns, the Spectral Swords, and the Imperial Uhlans, to forever be at the ready to render what aid they could to assist the others. Sadly as time wore on, the chapters would find themselves calling upon this aid with greater and greater frequency. First the Ashen Suns, the asteroid belt that housed their fortress monastery as well as the largest mining operation in the four neighboring systems falling prey to a genestealer cult uprising. The resulting campaign saw two companies of the Emperor's Sickle's deployed to the juxtaposing cramped mining shafts and vast void hardened surfaces in an effort to save as much of the Ashen Suns as they could before the Uhlans began seeding the asteroid belt with bioweapons. The loss of Ashen Suns marines, facilities, and geneseed was a blow significant enough to maim the chapter for generations.

Then two centuries later, the Spectral Swords fell, the system they stood sentinel over bending to the false promises of the Xenos t'au and their greater good. With a full six companies refusing to destroy the civilians they swore to protect, bloody civil war erupted and the surviving loyalist chapter members fled to the safety of imperial space, arming themselves for an ill fated crusade and calling upon their fellow chapters to aid them. To this struggle the Sickles committed a full five companies, with the Ashen Suns providing two and the Uhlans sending four. With the might of two armored regiments, a drop regiment, and five infantry regiments of the imperial guard aiding them, the remaining Spectral Swords suffered a mere six years before returning to their home system. Tragically, this was more than time enough for the foul xenos to fortify the planets and spaceways, as well as arm the willing humans and provide new equipment for the surviving traitorous marines. Blinded by rage at the image of their once proud citadels desecrated with T'au additions and supporting structures, All Four remnant companies ignored the pleas of their brothers and tore through the orbital defenses, taking horrific losses before planetfall. As the Spectral Swords purged the halls they once considered safe haven, it became sickeningly clear that the enemy commander had ordered the fortress garrisoned by turncoat humans, the very people they had sworn to protect. Once the loyalists had laid siege to the final layers of the fortress, the traitor marines launched their counterattack. Realizing their doom, the surviving Spectral Swords carved oaths upon the walls of their reclaimed home to take as many of their once-brothers with them as they could. After three days, the Imperial Fleet finally broke through the orbital defenses and hostile fleet. A task force of Emperor's Sickles from the third company approached the now ruined citadel in combat posture. To their dismay they discovered only a single living marine. Brother Malachai, the last of the Spectral Swords, his pulse weak, lying amongst a sprawl of his xenos serving brothers, his bolter emptied and fractured from being used as a club, his blade sunken deep into a throat of what appeared to be a mix of marine and battlesuit, and his gauntlets shattered as they bludgeoned a traitor captain into pulp. Even with such a strong Imperial presence, the Emperor's Sickles were forced to withdraw after ensuring that the system had ground to a standstill, for they had been called back home.

An Ork Waaagh, the size of which the subsector had never seen before, had surged forth from beyond Imperial space and now threatened the Chapter's home system. With the entirety of the Imperial Uhlans redirected to the Eye of Terror in order to repel the 13th Black Crusade, the Ashen Suns still reeling from the loss of their home two hundred years before, and the Spectral Swords all but extinct,the Emperor's Sickles would face this threat without their brothers. Yet they did not stand alone. The Forge World Alteo-Zenith delivered unto the Astartes Petitioners two macroclades of Skitarii and Cybernetica war machines. This force, alongside the system's PDF that had been personally trained by the marines composed of a force formidable enough to give even the greenskins pause, but still they pressed on. As the orks reached the Oort Cloud surrounding the system, deadfall boarding torpedos, loaded with dormant cybernetica and their hybernating datasmiths, triggered amongst the midst of the greenskin fleet. The already filthy gangways and corridors of the crude ships filled ankle deep with ichor as the automatons and their masters reaped a harvest worthy of legend before they fell, yet it was not enough. On the city moon of Ilyvich-6, fifty marines and twenty thousand mortal soldiers fought to the last, detonating archaic atomic stockpiles as the hated foe tore the armor from the final, laughing Astartes. Cunning crossfires and daring boarding actions allowed mankind the chance to slow the tide of blathering madness, but not stop it. Eventually the skies of Terek darkened with Ork ships and the Emperor's Sickles prepared to sell themselves dearly in the defense of their homeworld.

For two years the combined forces of Astartes, Mechanicus, and Planetary Defense Force waylaid the green tide. For two years every mile of Terek land was paid for with a funeral pyre of Ork corpses. Despite the weight of this toll, the invader paid it gladly and swallowed hole the Emperor's land, subjects, and even his angels. During the retreat from Zavodgrad hive, the entirety of the second company was caught in an uncharacteristic ambush. A warband of Flash Gitz and Lootas had waited for the marines to pull back, blowing charges on one of the few hive spires still standing. The avalanche of ferrocrete and steel pinned in the retreating astartes and the orks poured hellish amounts of fire into the killzone. Of the 86 Marines that began the retreat, less than 14 emerged intact. A desperate attempt at denying the Orks one of the planet's space ports had required three companies of astartes, and the resulting battle had consumed nigh on half their number. The defense of the fortress monastery consumed the entirety of the ninth and fifth companies. Putting all hope of a pyrrhic victory into one final gambit, Chapter Master Kovalyich led the chapter's entire surviving compliment of 60 terminators from the first company "Vympel" in a desperate decapitation strike at the heart of the Ork force. The warboss was deeply wounded, but the Chapter Master and nearly all that had followed had fallen as well. Realizing that they could not hope to retake their home, the surviving members of the Emperor's Sickle's, alongside the remnants of the Mechanicus Macroclades and PDF regiments, retreated from the planet and deployed cyclonic torpedoes. Employing a fabian strategy, they harried the Ork advance throughout the rest of the system with precise, fast strikes, strategic prolonged defenses, and fleet ambushes. Yet despite all the warcraft and talents at the disposal of successor Chapter Master Konstantinov, the imperial forces were steadily being pushed back, and after the results of the 13th black crusade, the Imperial Hierarchy refused to respond to all requests for assistance. With his home destroyed, his Chapter a shadow of its former glory, and his enemy triumphant and advancing, Konstantinov planned a final desperate attack.

Yet before he could begin, a massive fleet emerged from the warp on the system's edge. Hailing him was the Rogue Trader Masuda Arminius, the self proclaimed "Emperor's Condottiere", and alongside him the Chapter Master of the Ashen Suns and Brother Malachai, the last of the Spectral Swords. With forces from a score of worlds, some bought, some sworn to him, the Rogue Trader bade Konstantinov meet him in person. Bringing the blessings of Guilliman, Masuda brought forth Konstantinov into a great muster hall of his flagship, where awaited hundreds of Primaris, all adorned in the somber colors of the Emperor's Sickles. With his chapter renewed, Konstantinov swore a pact with the Rogue Trader to follow his fleet in their effort to save those pockets of humanity that the Imperium had not the resources nor desire to rescue formally. This oath was sealed in the fires of the retribution campaign that cleansed the Sickle's former home of the greenskin. On the still cooling fractured remnants of Terek, A kill-clade composed of the best of Masuda's forces struck at the incomplete fortress of the greenskin warboss. As Malachai himself took the head of the warboss, the bolters of Konstantinov and his contingent of Vympel Sternguard tore bloody chunks into the horde of greenskins pressing at the entryways of the throneroom while Ashen Suns Zanbato-adepts cleaved the swine-king's towering bodyguards. In the wake of vengeance exacted, Konstantinov understood that the Chapter's future lay with travelling alongside this fleet, smiting the foes of mankind where need arose. With this in mind, the chapter was renamed "Vityaz Errant" after the old Terra folktales of wandering knights.

After the catastrophic loss of 60% of the chapter on Terek, the Vityaz Errant begrudgingly readjusted their Chapter organization. The remaining 7 terminators were moved to the previously savaged Ninth company to serve as the backbone for the Primaris reinforcements who now filled its ranks. The most efficient killers from each company were reorganized to form two five man veteran squads, one to accompany the Captain as an honor guard, and one to act in a variety of roles as need be. Long holding hand to hand combat in contempt, the Second company was converted to a dedicated close combat unit, with squads or even individual marines being lent out to task forces as required. While these veteran squads were formidable in their own right, the proud remnants of the First company, "Vympel" only grew in their skill after the fall of Terek. Good fortune in the centuries that followed gave Vympel ample stocks of equipment and experience, allowing them to rival even the famed Deathwatch in skill and war panoply, albeit with far smaller numbers and less authority. Since then, it is not uncommon to see a Vityaz Errant task force enter a campaign with a roster from across the chapter. A unit of assault marines from the second, two squads of sappers from the sixth, tactical squads from the third and seventh, and, in the face of a great foe or historic undertaking, a handful of Vympel sternguard.