Manticore, whose real name is Sean Michael Fish, was part of the City of Heroes development team for a long time under Cryptic Studios, developing story and design since about a year before launch. Shortly after the City of Villains launch, he started working at NCSoft on a new MMO project; however, he remained in contact with the City of Heroes team.
Immediately after NCSoft purchased the City of Heroes' IP, it was announced that Sean Fish would once again be part of the design process of City of Heroes once it belonged solely to NCsoft. He remained with the newly established Paragon Studios for several years.
It was not announced when Fish left the company, but Matt Miller mentioned during one of the Lore AMA sessions that he had no longer been on the team when the first Signature Story Arc, Who Will Die was written, and was not consulted about having Manticore kill Sister Psyche.