Castinus was an Inquisitor of the newly created Ordo Hereticus when he led a quarantine team to search a missing Black Ship that was discovered in the Medrenax Nebula. Within it he found a bloodbath, as the Black Ship was filled with the mangled bodies of its crew and passengers, save for the powerful psykers known as the Apex Twins. When Castinus asked if they were responsible for the massacre aboard the Black Ship, the physically weakened Apex Twins readily admitted to doing so, without any hesitation. For reasons known only to himself, Castinus did not kill the Twins, perhaps because he was unknowingly influenced by their physic power, and instead brought them to the Inquisition fortress of Nemesis Tessera for analysis and study. This would have horrifying consequences, though, as the Apex Twins were able to regain their full power and freed themselves from their cells. What followed was a massacre, as the Twins began a murderous rampage that saw almost a thousand Inquisitorial troopers slaughtered as well as scores of full Inquisitors, before they made their escape. It is not known if Castinus was among those who were killed.