Tylos Rubio was an extremely powerful Space Marine psyker during the Great Crusade era of the early 31st Millennium, who had once been a Codicier of the Ultramarines Legion before the Emperor of Mankind’s formal decree at the Council of Nikaea had banned the Astartes Legions' use of psykers, including their own corps of Librarians. Honouring his oath to the Emperor, Tylos surrendered his Librarian panoply and wargear, and returned to the lines as an ordinary Battle-Brother. He would later be recruited by Nathaniel Garro, a former Death Guard Battle-Captain, during the infamous Battle of Calth at the outset of the Horus Heresy, and become one of the eight Astartes who would form the core of what would become the Grey Knights Space Marine Chapter.
During the opening days of the terrible conflict that would become known as the Horus Heresy in later years, the Warmaster Horus launched his treacherous attack on the world of Istvaan III against the Loyalist elements within four of the Space Marine Legions that had repudiated their oaths to the Emperor and turned to Chaos, including the Sons of Horus, the Emperor's Children, the World Eaters and the Death Guard. Having successfully purged the remaining Loyalists from the Traitor Legions, Horus plotted the next stages of his insurrection against his once-beloved father, the Emperor of Mankind. When word reached Terra of the Warmaster’s treachery at Istvaan III, as a result of the flight of the frigate Eisenstein under the command of Battle-Captain Nathaniel Garro and a small group of Loyalist Space Marines from the Death Guard Legion, the Emperor ordered the deployment of 7 Loyalist Astartes Legions to the Istvaan System to bring Horus to account for his actions.
It was while Horus made his plans for what would become known as the infamous Drop Site Massacre on Istvaan V, that the Warmaster sent word to the XVII Legion’s Primarch Lorgar that the time had come for his Astartes, the Word Bearers, to strike against the Imperium. The Warmaster was keenly aware of the bitter hatred that Lorgar had for his Primarch brother Roboute Guilliman and his XIII Legion, the Ultramarines, who had once humiliated the Word Bearers by destroying their city of Monarchia on the world of Khur at the Emperor's orders during the Great Crusade. Horus told Lorgar that he had fed Guilliman false intelligence in regard to a possible threat in the Segmentum Tempestus, far to the galactic south of Terra that stemmed from the Orks of the Ghaslakh Empire. Horus had ordered the XIII and the XVII Legions to muster and meet at the world of Calth in the Ultramarines' Realm of Ultramar, in order to conduct a massive joint campaign of extermination against the Ghaslakh xenohold, a common mission for the Astartes during the final days of the Great Crusade.
It would be at Calth that Lorgar would launch a surprise attack on the Ultramarines whilst they were gathered for the campaign against the Orks of Ghaslakh that would never begin. The XIII Legion would be caught completely unaware while the Word Bearers seized the advantage of surprise to completely annihilate their hated rivals. This treacherous campaign would come to be known as the Battle of Calth or the Calth Atrocity. There were many portents of the tragedy soon to unfold upon Calth. Given the extraordinary thoroughness with which the XIII Legion maintained its readiness, it might have been considered tragic, or incompetent, that so few were heeded. Before the attack on Calth, those gifted with psychic abilities suffered severe headaches and pain behind the eyes. One such gifted individual was Tylos Rubio. He ignored the mysterious pain, chalking it up to nothing more than fatigue after having gone without rest for several days during the preparation phase for the coming campaign against the Orks. It had not been possible to shut down higher mental functions and sleep, or at least remedially meditate, a common form of rest for the genetically-engineered Astartes. This mysterious pain was actually a warning sign broadcast through the Warp of the impending approach of the Forces of Chaos. But Rubio and all of his former Librarian comrades ignored the headaches. Few would survive the coming assault long enough to regret it.
Battle of CalthEdit
After arriving in the Sol System with the terrible news of the Warmaster's betrayal, Garro, his fellow Death Guard Astartes and a number of other Loyalist refugees, were all placed in a fortress on Luna that belonged to the Sisters of Silence whilst the Emperor determined whether they were truthful or were simply further pawns of the Chaos Gods. Garro was eventually approached by Malcador the Sigillite, the acting Regent of Terra, who told him that the Emperor needed men like him to help form a new Imperial organisation outside the boundaries of the existing Imperial bureaucracy. Under the Sigillite's own seal, Garro was tasked with finding 7 other Loyalist Astartes from amongst both the Loyalist and Traitor Legions who were utterly devoted to the Emperor and his Imperium in body and soul. These Space Marines would eventually form the core of what would later evolve into the Grey Knights Chapter of Astartes, the Chamber Militant of the Inquisition's Ordo Malleus.
Garro’s first mission was to war-torn Calth, a battle-scarred Agri-World located in the Veridian System. The Loyalist XIII Legion, the Ultramarines, were engaged against their treacherous former brethren from the XVII 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. 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." 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 had managed to rally 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 XIII Legion before the Emperor’s formal decree at the Council of Nikaea had banned the Space Marine Legions' use of psykers, including their corps of Librarians. 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 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. Yet 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 Battle-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 Power 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.
Several years later, Tylos Rubio accompanied Garro, and another Loyalist Astartes, a former World Eaters Captain named Macer Varren, to the devastated world of Istvaan III, to recruit the seventh and final warrior of their new fellowship -- Garviel Loken, a former Captain and member of the Mournival of the Sons of Horus. Though Istvaan was now a barren graveyard planet, appearing devoid of all life, somehow Loken had survived the Traitor's final orbital bombardment and eked out a bleak existence on the planet's blighted surface amongst the ruins of the capital of Choral City for several years. 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 champion of the Emperor and Loyalist in the galaxy until he was confronted by Garro and his fellow Astartes.
After their arrival on the surface of the planet by Thunderhawk, Rubio, Garro and 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 Istvaan III, and on discovery of the long-dead headless corpse of Tarik Torgaddon, he was attacked by the unkempt, nearly-psychotic "Cerberus." During his fight with Loken, Varren urged the mad Astartes not to endanger the civilian refugees nearby. Garro wanted to put the insane Astartes out of his misery, but Varren argued that they had already lost too many brothers to Horus' treason. After a lengthy battle, during which Cerberus escaped, Garro and his companions discovered that the human "survivors" of the virus-bombing of Istvaan 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 Istvaan 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 mistakenly 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 Istvaan III, Garviel Loken joined Garro and his team. With his assemblage of warriors now complete, Garro and Loken left Istvaan III for Luna to receive their first mission from Malcador the Sigillite. Rubio's fate after the Horus Heresy remains unknown.
- Garro: Oath of Moment (Audio Book) by James Swallow
- Garro: Legion of One (Audio Book) by James Swallow
- Know No Fear (Novel) by Dan Abnett