Tolbek was a member of the XVth Legion during the great crusade, was an adept of the Pryrae cult, and had risen to the rank of sergeant during the Space Wolves devastating attack on the Thousand Sons' homeworld. Tolbek fought to defend the streets of Old Tizca, where he and his squad managed to destroy a Space Wolf Leviathan-class Dreadnought before being pushed back. Leaving half of his squad behind, Tolbek and a handful of other Pyrae members retreated to their temple, and managed to secure several ancient works from the archives there before Khalophis, the cult's leader, lost control of the titan Canis Vertex, consuming his soul and causing the temple to collapse. As ethereal flames consumed the room he was in, Tolbek heard a voice in his head, begging him to save one final book from the fire. Rushing back into the Archives, Tolbek found the book he was searching for, but was trapped under a falling statue as he attempted, along with another member of his squad, to escape. Badly wounded, he managed to remove his armour and escape. Retreating to the center of Tizca along with the rest of his legion, Tolbek, clad only in his black undersuit, was ambushed by the Vlka Fenryka. He once again escaped, although he had no recollection of how he did so. Losing consciousness, he was once again visited by the echoing voice. After coming to, the entire squad of Space Wolves lay surrounding him, their bodies burned to a crisp. The voices returned, this time telling Tolbek they would protect him from all harm, but they required a price. Tolbek managed to return to the center to Tizca without further incident, but played no further part in the battle until the Space Wolves managed to penetrate the Thousand Sons' defences and began their assault on the Great Library. Tolbek then returned to the front line, assisting his brothers and finally protecting Ahriman as he attempted to save their legion.
After their escape to Soritarius, Tolbek agreed to help Ahriman cast a spell that would prevent the Thousand Sons from mutating. After Magnus' return, Tolbek, Amon and a psychic double of Ahriman left the Planet of the Sorcerers and returned to the Prospero sector. They managed to locate a task force of Thousand Sons that had left Prospero before the battle, and along with a delegation from Zhao Arkhad traveled to the planet Aghoru, a planet they had captured shortly before they were banished. Ahriman and Tolbek inspected the xenos device known as the Mountain. They both entered the same cave their primarch had disappeared into, and found themselves in a long tunnel that seemed to break every law of physics and geometry. Following Ahriman, Tolbek descended a set of ghostly stairs and arrived at what appeared to be a simple archway, but made of a substance reminiscent of bone. The passed through the archway and found themselves in the material realm again. Tolbek managed to glance around himself before losing consciousness again. The voices returned, telling him to remain calm and trust the one he saw first upon opening his eyes. After he came to, he found himself surrounded by xenos wearing blue and green, flanking a tall figure wearing a flowing cape and pointed helmet. Sensing immense psychic power, and heeding the voices advice, Tolbek dropped to a knee and bowed to the xenos.
He and Ahriman spent several days with the xenos, who called themselves Eldar. They learned of the portal they had passed through, called the Webway, and of the Emperor's plan to use it for his own plans. They also learned of the Eldar's own story, most notably the history of their fall and the escape of the ship they were on, named Mymeara after their ancient Homeworld. They, according to the Eldar farceur telling the story, once thought themselves to be the last Eldar in existence, until a powerful warrior named Irillyth. He had saved the craftworld from destruction by defeating another xenos race, but had fallen in the process. However, not all hope had been lost, since Irillyth's soul remained trapped in the armour. This interested Ahriman immensely, and he begged the farseer to help him locate the armour. After several days, the Farseer relented, and sent a younger fareer named Theàrlaich Dushkriti and a taskforce of Eldar soldiers, among them several Wraith constructs. These creatures interested Ahriman as well, as, although they were dead, still could communicate with their comrades. They returned through the Webway to Aghorou, but found their allies surrounded by space marines from the Death Guard legion, lead by Calas Typhon. Ahriman and the eldar pushed the enemy legionaires back, and Tolbek face off against Typhon, aided by Theàrlaich. They managed to wound Typhon badly, but he escaped by teleporting before they could strike the killing blow.
Ahriman and the rest of the remaining Thousand Sons, along with the Eldar and several psychic Aghorouians, managed to cast a spell allowing them to locate Irillyths armour on an ice world far from Aghorou. The Eldar then retreated into the Webway, leaving the Thousand Sons to continue their mission: kill Horus, the Wrmaster, and return to their rightful place ate the Emperor's side.