*Frank Horrigan was born in 2211. A huge brick of a man, he used to serve as the personal bodyguard of President Dick Richardson until an undocumented psychotic blunder caused him to be reassigned to wasteland patrol duty. It was on one of those wasteland expeditions that he came into contact with the Forced Evolutionary Virus at the Mariposa Military Base and started mutating into a super mutant.

The Enclave decided to send him to the Oil Rig for study. Exposure to FEV and subsequent experiments made him bigger, stronger and faster than any other super mutant. His armor continually injects him with drugs and other stablizing agents, and is the only thing keeping him alive. He was also fitted with several cybernetic enhancements, including arm control mechanisms, leg rotator mechanisms, and a bionic eye. Despite his appearance, Horrigan didn't consider himself a mutant, referring to other wastelanders as "muties" instead.

He was a mutant only to the Enclave scientists, mostly referred to as an "experiment." Among soldiers, he was considered a curiosity built by the science team, a freak that few were willing to accompany on missions in the field. Horrigan was extensively deployed to the wasteland, tasked with resolving any situations that may affect the Enclave. He indulged his sadistic streak, and the manner in which he killed "mutants" was brutal enough to give lasting nightmares to the Enclave troops supporting him. None lasted more than 60 seconds, allegedly.

One such assassination occurred on August 30, 2241, he was tasked with hunting down and recruiting an elderly farmer whose knowledge could prove dangerous, killing him without a second thought when the man refused. The Chosen One had the dubious privilege of witnessing the execution. Horrigan spared him and merely left, a costly mistake in hindsight. He also killed Matthew at the San Francisco Brotherhood bunker following his acquisition of Vertibird plans.*