Nathaniel Garro - Agentia Primus: After arriving on Terra at Malcador the Sigillite's invitation to begin his quest as the Sigillite's new Agentia Primus, Garro's power armour had all of its Death Guard regalia removed and replaced with the personal sigil of Malcador, a stylised letter "I" with three horizontal lines through its centre, the icon that would later become infamous across the galaxy after the Heresy as the Rosette of the Inquisition.During his mission for the Sigillite, when questioned as to which Legion he belonged to, Garro consistently referred to himself as a "Knight-Errant" and the member of a "Legion of One." Garro's first mission was to the war-torn Calth, a battle-scarred Agri-world located in the Veridian System.The Loyalist XIIIth Legion, the Ultramarines, were engaged against their treacherous former brethren from the XVIIth Legion, the Word Bearers, in a great contest of the Heresy known to history as the Battle of Calth.Garro slipped past the Word Bearers' orbiting fleet and down to the surface of the war-ravaged planet. He was looking for the Ultramarines' 21st Company, under the command of Captain Erikon Gaius. The 21st Company had been last sighted on the western outskirts of the city of Numinus.They had been at the forefront of the first Word Bearers assault and it had been their burden to witness the deaths of too many of their battle-brothers at the hands of the Traitors and their daemonic allies. They were now a company in name only.Their captain -- the Hero of the Hadier Uprising, Gaius the Strong, Gaius the Unflinching, had rallied them in the face of the brutal losses. With words and deeds he had led them into the fray, and they claimed back in blood a steep price from the Traitors, but not enough. They were cut off from their kinsmen, holding one of the mag-lev railroad approaches to Numinus City.Garro sought out Battle-Brother Tylos Rubio amongst the Astartes of the 21st Company, an extremely powerful psyker who had once been a codicier of the XIIIth Legion before the Emperor's formal decree at the Council of Nikaea had banned the Space Marine Legions' use of psykers, including their own corps of Librarians.Many resented the Decrees of Nikaea, but honoured their oath to the Emperor and surrendered their Librarian panoply and wargear, returning to the battle lines as ordinary battle-brothers.Captain Gaius had been killed in a Word Bearers' assault when a large force of Traitor Marines and Chaos Cultists nearly overwhelmed the 21st Company's battle lines. Garro arrived before the next assault and found Brother Rubio. He explained to the perplexed Ultramarine that he was there on the orders of Malcador the Sigillite and that Rubio must come away with him.Rubio refused to leave his battle-brothers in the face of annihilation unless so ordered by the Emperor Himself. Much to Rubio's surprise, the honourable Garro respected his decision and agreed to stand and fight with him against the Word Bearers.In the final assault, the Ultramarines were driven back in the face of overwhelming numbers, and sought cover within a cave. They were hard-pressed by the elite Word Bearers' Cataphractii-armoured Terminators.Brother Rubio was sorely tested, forced to restrain from using his innate psychic abilities, bound by his sacred oaths to the Emperor, even though he knew that by doing so he could have saved the lives of many of his fallen battle-brothers.Facing imminent death, Rubio felt that he had no other choice and unleashed a powerful psychic attack, driving the enemy back with the full force of his powers. The tunnel collapsed in the process, burying the attacking Word Bearers Cataphractii under tons of rubble.The survivors of the 21st Company had been saved and the sole passage to Numinus had been denied to the enemy. But the cost of using his powers had cost Rubio dearly -- his honour before his primarch and his Emperor. Garro told him to be grateful that he had saved his brothers' lives.As he approached his fellow Ultramarines, they averted their eyes and as one turned their backs, shunning him. Rubio had disobeyed a Decree Absolute of the Emperor, and for that, there was no forgiveness. Garro drew his sword Libertas and Rubio spun at the sound of it, fixing Garro with a furious glare.Garro held the sword out, the point down towards the ground. He had Rubio place his hand upon the blade to take an Oath of Moment, to dedicate himself to the orders of the Regent of Terra and put aside all other claims upon his honour. Rubio swore upon the blade, for he had little other choice.The next Astartes that Garro recruited was Captain Macer Varren, a former battle-brother of the XIIth Legion, the World Eaters, who had turned Traitor to the Emperor and followed Horus in his madness. Like Garro and his fellow Death Guard warriors, Varren too, had forsaken his own kinsmen after they swore fealty to the Warmaster and the Dark God Khorne.The lord of his Legion, the gladiator Primarch Angron, had sent his personal guard to kill Varren for his refusal to join the World Eaters in their sedition against the Emperor. Varren escaped with his life, and an embittered heart.Varren was recruited into the Knights-Errant shortly after Garro returned to Terra with Rubio. As they entered the Sol System, Garro was ordered by the Custodian Khorarinn of the Legio Custodes to accompany him to deal with a ragtag fleet of vessels led by the Daggerline that had arrived on the edge of the Sol System.Aboard were members of the Emperor's Children and White Scars Legions led by Captain Macer Varren of the World Eaters, who had also abandoned his Legion after refusing to turn against the Emperor. These Astartes claimed to be Loyalists, but the Legio Custodes distrusted their motives and believed they might be Traitor infiltrators. After the White Scars proved to be Traitors, the Daggerline was destroyed, but Varren joined the Knights-Errant.Garro had offered him a new role as one of Malcador's Knight-Errant operatives, but in truth, the duty sat poorly with him. Quick to anger like all World Eaters, he longed to be out in the thick of the war, facing his former battle-brothers. He lacked the cool detachment of the Death Guard or the stoicism of the Ultramarine Librarian Tylos Rubio.While in the Sol System, Garro also infiltrated the Imperial Fists' mobile fortress-monastery Phalanx in an attempt to recruits the Codicier Yored Massak, who had been sealed in a vault with the other Librarians of the Imperial Fists in accord with the Decrees of Nikaea.Massak refused the offer, and the Imperial Fists Primarch Rogal Dorn warned Garro to be wary of the Sigillite's orders. Dorn's warning led Garro to discover that his Apothecary, Meric Voyen, one of The Seventy, had recovered the remains of the Daemon-possessed Solun Decius on Luna and was taking them to Io, the moon of Jupiter, for study. Garro intercepted the ship, diverting its course towards Io to jettison the Chaos-tainted remains into the sun.Garro then resumed his recruitment mission, working his way down a list compiled by Malcador and Severian, a Luna Wolves psyker who had also been recruited into the Knights-Errant.In 017.008.M31 Garro arrived in the Pale Stars aboard the Warp-sprinter called the Eusebeian Herald, accompanied by Tylos Rubio and Callion Zaven, and sent out a coded signal from Optera IV.Captain Serron of the Blood Angels, Nirun of the White Scars, and the mysterious Blackshield known only as the Nemean Reaver of the Dark Brotherhood answered his summons, but the conclave was interrupted by an Alpha Legion ambush. The Knights-Errant teleported aboard the Eusebian Herald, taking the Nemean Reaver -- their originally intended recruit -- with them.The last of the seven warriors that Garro was ordered to recruit was Garviel Loken, once a captain and member of the Mournival of the Sons of Horus. Though it appeared that he had perished during the final bombardment on Isstvan III, he had somehow managed to survive on its blighted surface in the ruins of the Choral City for several standard years after the Traitor Legions had moved on and the larger tragedy of the Horus Heresy had consumed the galaxy.The Warmaster's insurrection had long since moved onwards towards other sectors. The world of Isstvan III was now a desolate and barren graveyard planet inhabited only by Plague Zombies raised by the lingering taint of Nurgle which had consumed the world after the Life-Eater virus had destroyed all life upon its surface.Loken had been driven mad by the horrors he had experienced and believed that he had been rejected by Death itself. He experienced a form of amnesia and could no longer recall his own name, taking upon himself the new identity of "Cerberus," believing himself to be the sole remaining Loyalist in the galaxy and champion of the Emperor until he was confronted by Garro.After their arrival on Isstvan III by Thunderhawk, Garro, Rubio and Macer Varren encountered a handful of what they believed to be Human survivors who spoke of a beast that hunted them.Taking matters into his own hands, Garro went to the lair of the so-called beast of Isstvan III, and on discovery of the long-dead corpse of Tarik Torgaddon, he was attacked by the unkempt, nearly-psychotic "Cerberus."After a lengthy battle, during which Cerberus escaped, Garro and his companions discovered that the Human "survivors" of the virus-bombing of Isstvan III were in fact Daemonhosts who had been transformed into undead Plague Zombies of Nurgle when the virus-bombing had weakened the barrier between the Immaterium and Isstvan III, allowing the Plague Lord's influence to reign supreme.Garro and his Loyalist Astartes managed to defeat the foul creatures with the aid of Cerberus; however, once the undead had been destroyed, Garro and Cerberus had one more one-on-one combat match, as Loken perceived the group of Astartes as Traitors who had come to kill him.It was during this final fight that Garro managed to reach through the amnesia and fractured awareness of Cerberus to the core of the good man that remained deep within his psyche, reminding him of who he truly was, and that the Emperor still had a use for him in rooting out the corruption that was staining the Imperium.Aware of his true identity once more and how he had come to be stranded amidst the ruins of the Choral City of Isstvan III, Garviel Loken joined Garro and his team.With his assemblage of warriors now complete, Garro and Loken left Isstvan III for Luna so the Knights-Errant could receive their first mission from Malcador the Sigillite.