Cato Sicarius was born into the ducal household of Talassar, one of the proudest noble dynasties of the Realm of Ultramar, and something of that highborn confidence has never left him. Raised into the Ultramarines and swiftly marked as a warrior of rare talent, he rose to command the storied 2nd Company, becoming one of the most celebrated, and most divisive, captains in the Chapter's long history.
His list of honours is extraordinary. Sicarius earned the Imperial Laurel for his conduct at the Crusat Minor planetstrike, the Honorifica Valorum after the Battle of Dyzanyr, and the rarely granted Valour Crest for near-suicidal heroism during the nine-day fight for Fort Telendrar. In the tunnels of Black Reach he cut down the Ork warlord Zanzag, and on the frozen world of Damnos he broke the legions of the Sautekh Necrons and helped banish a fragment of a star-devouring C'tan back into the darkness.
Yet for all his brilliance, Sicarius is a proud and ambitious man, his self-assurance verging at times upon arrogance. His unorthodox tactics and open hunger for glory have earned him rivals within the Chapter's officer corps, even as his results silence most criticism. His fierce rivalry with Severus Agemman, First Captain and Regent of Ultramar, is well known throughout the Chapter, a contest of pride between two very different visions of what an Ultramarine ought to be. In battle he wields the Talassarian Tempest Blade and the plasma pistol known as the Talassar Bolt, a whirlwind of aggression who leads always from the very front.
When Roboute Guilliman returned and marched to relieve Terra, it was Sicarius he chose to lead the Victrix Honour Guard, entrusting his own safety to the captain's peerless skill at arms. In the wars of the Indomitus era that followed, Cato Sicarius has continued to burnish a legend that he, more than any, is determined the Imperium shall never forget.