- "We are the slayers of kings, the destroyers of worlds, bringers of ruination and death in all its forms. These things we do in the name of the Emperor and in the defense of Mankind. Let none stay our wrath."
- — Captain Cato Sicarius, Ultramarines 2nd Company
Cato Sicarius is the current Captain of the Ultramarines 2nd Company. His titles include Master of the Watch, Knight Champion of Macragge, Grand Duke of Talassar and High Suzerain of Ultramar. He is known as one of the greatest of the Ultramarines' heroes, and is also said to be the heir apparent to Marneus Calgar, the current Chapter Master of the Ultramarines and the Lord of Macragge. Each of these honours reflects only a fragment of an entire lifetime of diligent and extraordinary service to the Realm of Ultramar and the Emperor of Mankind.
Having been born into one of the ascendant noble houses of the world of Talassar in the Realm of Ultramar, Sicarius was trained in martial combat as soon as he was old enough to wield a blade, as is the way of the Talassari nobility. This tutelage in the ways of war was only reinforced by his later induction and training amongst the Ultramarines Chapter. When he was recruited into the Ultramarines, Sicarius earned commendation after commendation and rose swiftly through the Chapter's ranks. In the decades that followed, he served as Sergeant and then 2nd Company Champion before ultimately assuming the command of the 2nd Company himself.
Only the most accomplished of warriors could hope to command the Ultramarines 2nd Company and Sicarius rose to that challenge as he had to all the others in his life. All Astartes make use of the lightning assault as their preferred combat doctrine, but Sicarius refined this tactic to near-perfection and often committed his forces to combat with only the briefest appraisal of the tactical situation. In another man, such haste might seem reckless or unwise, but Sicarius possessed an unparalleled ability to adapt to the chaos of war and proved capable of easily marshalling his forces and seizing the advantage in almost any combat situation. Sicarius' assaults always took a fierce toll amongst the foe, in both numbers and morale. Even other Astartes were often left in awe by the sheer speed with which Captain Sicarius could analyse and then react to a rapidly-evolving tactical situation.
After being raised to command of the 2nd Company, Sicarius' first combat action took place during the Dantaro Campaign. In the course of his service to the Chapter, Sicarius earned a wide variety of battle-honours, including the Imperial Laurel after the Crusat Minor Planet Strike in 733.M41, the Honorifica Valorum after the Battle of Dyzanyr, and the Valour Crest following the Battle for Fort Telendrar. Amongst the political positions awarded to Sicarius as a high-ranking officer of the Ultramarines was that of Grand Duke of Talassar, his homeworld, and Suzerain of Ultramar in 849.M41.
Sicarius commanded the Ultramarines strike force that faced the Forces of Chaos during the Battle of the Halamar Rift and his Strike Cruiser Valin's Revenge and its Escorts managed to defeat most of the Chaotic warfleet. However, after the Ultramarines boarded the main Chaos warship, Sicarius failed to kill the Daemon Prince M'kar, who fled back into the Eye of Terror to prey upon the Ultramarines again at a later date.
Perhaps the most famous action Sicarius ever participated in was the Assault on Black Reach when the Ultramarines faced off against the WAAAGH! of the Ork Warlord Zanzag. The entire Ultramarines 2nd Company was deployed against a force numbering some 10,000 Greenskins. When the Astartes ultimately ran out of ammunition against the savage xenos, Sicarius ordered them to use Combat Knives and Chainswords until every last Greenskin had met its end. Only a single Terminator and 12 Space Marines from the 2nd Company were slain during the Ultramarines' operations on Black Reach.
In 974.M41, on the resource-rich Mining World of Damnos, which was also a Necron Tomb World, Sicarius led an Ultramarines assault against the Necrons who had awoken from their hidden tombs on the planet and now threatened to overrun it and its small Imperial military garrison. To combat the Necrons' undying threat, Sicarius split the 2nd Company into three separate forces. He led the largest against the main part of the Necron force that assaulted the outer walls of Kellenport, the planetary capital city. Sicarius was wounded during the combat by the War Scythe of the Necron Lord, but was rescued by his Astartes and evacuated to his orbiting Strike Cruiser. Damnos was deemed unrecoverable by the Imperium, but the Ultramarines managed to evacuate a portion of the planet's remaining human population and then launched an airstrike on a very unstable geothermal power reactor within the planetary capital city of Kellenport which detonated and cleansed the Necron presence, if only for a time. This course of events became known as the Damnos Incident and that world is now classed as a possession of the Necrons and is a Forbidden World of the Imperium.
Sicarius commanded the Imperial operations during the Fall of Medusa V in 999.M41 and deployed his forces across the world to take up defensive positions before finally giving the order for an Exterminatus of the planet following a long and bloody campaign.
Captain Sicarius led his company and the forces of 30 other Space Marine Chapters and Imperial Guard Regiments during the Zeist Campaign in 999.M41 against the forces of the Tau Empire, which were seeking to expand into Imperial space on the Eastern Fringes of the galaxy. By the time the Imperium moved to counter the Tau expansion, 26 Imperial worlds had already been claimed by the servants of the Greater Good. The forces of the Imperial Guard and contingents of Astartes from the Night Watch, Halo Dragons, Silver Skulls, Crimson Fists and other Chapters joined Sicarius and his Ultramarines on the world of Praetonis V to coordinate the Imperial defence and counteroffensive. Sicarius chose to deploy his forces using the same tactics of mobility and precisely targetted firepower that had allowed the Tau to claim so many successes. The combined Imperial strike force reclaimed all of the 26 planets that had been annexed by the Tau and badly blunted the Tau's offensive, forcing them to delay their 4th Sphere Expansion until they recovered from the heavy defeat inflicted by the Zeist Campaign. But before the Imperium could launch a full counter-invasion of Tau space, the High Lords of Terra recalled the force to deal with the onslaught of the 13th Black Crusade.
When Sicarius and the 2nd Company returned to Macragge in 854.999.M41 they discovered that the Realm of Ultramar had come under assault by the Forces of Chaos led by the Daemon Prince M'kar the Reborn. The entire Ultramarines Chapter was despatched to protect all the worlds of Ultramar that were under attack, while Marneus Calgar joined Sicarius and the 2nd Company to defend Sicarius' storm-wracked homeworld of Talassar from the Chaotic assault. After a fierce campaign, M'kar was finally slain and banished back to the Warp by Calgar, who promised that he would slay the foul Daemon Prince a hundred times more if such was required to keep Ultramar and the Imperium safe from his corruption.
In time, Cato Sicarius' very name became a byword for Imperial victory, a legend that came to the ears of allies and foes alike far beyond the borders of Ultramar. At the close of the 41st Millennium, the Ultramarines 2nd Company always draws the most dangerous missions assigned to that Chapter and Sicarius is believed by most Ultramarines to be a fitting heir to become the Ultramarines' Chapter Master and Lord of Macragge when Marneus Calgar finally passes to join the Emperor. This sentiment amongst his comrades probably does not sit quietly with Severus Agemman, the Captain of the Ultramarines 1st Company and the current Regent of Ultramar.
Cato Sicarius is known to wear a special suit of Artificer Armour known as the Mantle of Suzerain that provides a level of protection equivalent to that of a suit of Terminator Armour. The left pauldron of this armour belongs to the original suit of Mark II Crusader Power Armour worn by Captain Orar, a great hero of the Ultramarines Legion during the Scouring of the Traitor Legions from Imperial space after the end of the Horus Heresy and a former Captain of the 2nd Company. It bears the 2nd Company's heraldic colours which Sicarius has also adopted as his own personal heraldry and also incorporates an Iron Halo and a Golden Aquila that designates his position as the Grand Duke of Talassar, his homeworld. Sicarius' helmet is topped by a horizontal Valour Crest that was granted for near suicidal acts of bravery during the nine-day-long battle fought for control of Fort Telendrar. The colours of the crest match those of the Talassari noble house from which Sicarius was recruited as an Aspirant into the Ultramarines centuries ago.
Sicarius prefers to wield a potent Power Sword known as a Talassarian Tempest Blade in close combat. The weapon's energy field is so strong that in certain instances it can slay a foe with a single strike. For ranged combat, Sicarius makes use of an Artificer-crafted Plasma Pistol.
- Aquila - The Aquila is an Imperial Honour Badge shaped in the form of the Imperium's own crest that proclaims its wearer's great wisdom. It was awarded to Sicarius at the commencement of the Dantaro Campaign, which represented Sicarius' first action as Captain of the 2nd Company.
- Eternium Ultra - There are few such revered relics in the Realm of Ultramar as these gardbarces. They mark Sicarius as the High Suzerain of Ultramar and defender of the eight systems of Ultramar.
- Imperial Laurel - This Imperial Laurel was awarded to Sicarius in the wake of his service in the Crusat Minor planetstrike of 733.M41.
- Honorifica Valourum - Awarded in recognition of exceptional bravery when fighting Orks during the Battle for Dyzanyr.
- Personal Heraldry - Sicarius' left shoulder plate originally hails from an ancient suit of Mark II Crusade Pattern Power Armour worn by the Ultramarines Legion hero Captain Orar during the Great Scouring of the early 31st Millennium. The heraldry combines the Iron Halo, the Ultramarines Chapter icon and the golden Aquila that marks Sicarius as the Grand Duke of Talassar.
- The Valour Crest - The right to bear a crest upon one's helmet in the Ultramarines Chapter must be earned through acts of near suicidal bravery. Sicarius won his crest during the nine-solar-day long battle for Fort Telendrar. The colours of the crest are those of the Ultramarran noble house from which Sicarius was recruited, countless decades ago.
- Victorex Alpha - This honour, attached to Sicarius' combat skirt, was granted in recognition of his exceptional valour during the Siege of Rynneth V.
When Marneus Calgar travelled to Talassar after M'kar the Reborn's attack upon the Realm of Ultramar in 999.M41, the Codex: Space Marines (5th Edition) makes clear that Calgar accompanied Sicarius and the Ultramarines 2nd Company to that world. However, in the novel The Chapter's Due by Graham McNeill, Calgar travels to Talassar with the Ultramarines 1st Company led by Captain Severus Agemman. The 2nd Company did not arrive at Talassar in the novel until first concluding their own campaign against the Forces of Chaos on the Cardinal World of Espandor.
This was later explained away by the Black Library which explained that Games Workshop maintains multiple different canons in the Warhammer 40,000 universe and that the only truly official canon is found in the various Codexes.
- Codex: Space Marines (6th Edition) (Digital Edition), pp. 82, 97, 346-349
- Codex: Space Marines (5th Edition), pp. 19, 22, 40, 85
- Warhammer 40,000 Rulebook (5th Edition), pp. 18-19, 22, 36-40, 85, 129
- White Dwarf 317 (UK), "Medusa V Campaign"
- Fall of Damnos (Novel) by Nick Kyme