Originally a Sergeant in the 4th Company of the Sons of Guilliman Chapter, Constantinus and his squad fought to free the population of the world of Nova Terra from Tyranid attack. After driving the aliens off the world, his unit was left behind to monitor for signs of Genestealer infestation. For three standard years Constantinus led his squad on endless patrols through the caves of Nova Terra, cleansing the planet of the remaining pockets of Tyranid infestation. When rumour arose of a Genestealer infestation among the city of Cirtus' ruling aristocracy, Constantinus brutally hunted down the infected nobles and their families.