On the day they were supposed to be executed, they instead became victims of the fifth laboratory's horrid human experiments involving the removal of souls from the bodies of nearby Central Prison's death row inmates. They had their souls bound to a single suit of armor by way of a pair of blood runes (one in the helm and one in the armor's neck piece) and were assigned to kill any intruders at the laboratory. Prior to their official "execution" about two years before the start of the series, they were known about the country of Amestris as the infamous serial killer "Slicer" who, when finally captured, was discovered to have been a pair of murdering brothers.