Upon being recruited by Destro, Dr. MacGregor began a database search to find new subjects for his experiments. He combed through the files of all associated with both MARS Industries and the Iron Grenadier ranks searching for key genetic markers, psychological qualities, and violent behaviors. He selected these individuals and conducted psychological and nana technological experiments. The end results were elite troopers known as Iron Skulls. With all fear, most traces of humanity gone, these troops operate with a hive like mind.