Beyreuth was the Chief Custodian and Captain-General of the Adeptus Custodes during the War of the Beast in the mid-32nd Millennium. Following that campaign, Beyreuth became the first Captain-General of the Adeptus Custodes since Constantin Valdor to take up a seat on the Imperium of Man's ruling body, the Senatorum Imperialis, and to willingly engage in the process of ruling the domain of Mankind.
Little is known of the early history of the Custodian known as Beyreauth or when he ascended to the esteemed rank of Captain-General. What is well documented are his actions during the crisis which came to be known as the War of Beast in the mid-32nd Millennium. At that time, he led the Custodian Guard in battle against the Harlequins of the Troupe of Joyful Tears, when they managed to breach the sanctity of the Imperial Palace, intent on personally delivering a message to the Master of Mankind. Only Shadowseer Lhaerial Rey and Death Jester Bho reached the chamber that led to the Sanctum Imperialis. They were able to kill dozens of Custodians, all the while as the Shadowseer insisted that she had come in peace. She explained that she had been sent on behalf of the notable Ulthwé Farseer Eldrad Ulthran to deliver an important message to the Emperor. But the Adeptus Custodes would not relent in their sworn duties, and so the Custodians pressed their attack against the xenos interlopers, killing Bho and impaling Lhaerial to the ground with a Guardian Spear. As the Shadowseer continued to insist on meeting with the Emperor, the enraged Captain-General was about to give the order to kill her, until the timely intervention of Inquisitor Lord Veritus saved the Harlequin's life.
In his capacity as the Inquisitorial Representative to the Senatorum Imperialis, Veritus forced Beyreuth to release Lhaerial to him so that he could interrogate her. After the tragic event known as The Beheading occurred, the de facto rule of the Imperium fell to the sole remaining High Lord of Terra, the Officio Assassinorum's Grand Master of Assassins, Drakan Vangorich, who reminded Beyreuth of the fact that the Eldar had nearly breached the threshold of the Eternity Gate. This argument convinced Beyreuth to engage in Imperial politics and take his place amongst the esteemed ranks of the Senatorum Imperialis alongside Vangorich.
- War of the Beast Book Five: Throneworld (Novel) by Guy Haley
- War of the Beast Book Twelve: The Beheading (Novel) by Guy Haley