Chris Redfield is an American Special Operations Unit operator in the Bioterrorism Security Assessment Alliance, in which he has served since its foundation in 2003. Redfield has built up and dedicated his career in destroying Bio Organic Weapons and fighting against producers and sellers of bioweapons after his experiences with bioterrorism in 1998.

Piers Nivans is a soldier in the Bioterrorism Security Assessment Alliance (BSAA), a UN-controlled military devoted to combating bioterrorism. A former soldier in the US Army, Nivans was placed in the BSAA's Special Operations Unit within the North American branch. Throughout his career, Nivans served under Cpt. Chris Redfield, whose high security rating allowed the two to participate in investigations outside of North America.

Tom Berenson is the older brother of the leader of the Animorphs, Jake, and the reason Jake joined the fight against the Yeerks. He spent four years as a host body for a Yeerk called Temrash 114. One day, when Temrash 114 went to the Kandrona pool to feed, he was freed from his cage by the Animorphs and helped them free other hosts before trying to escape.

Unknown to Clint Barton, founding member of the Avengers and special agent of SHIELD, the hidden world of the supernatural has taken an interest in his younger twin. He and his brother, IMF agent William Brandt, became orphans after their parents were lost in a car crash. Both brothers ran away and joined the Circus of Crime, Will keeping the books and Clint being trained by Buck Chrisholm. Now Clint and Will must navigate a world they’re not fully aware of. Clint is unmarried and never had any kids.

Clinton Francis "Clint" Barton is an extremely skilled marksman, a special agent of S.H.I.E.L.D. and one of the founding members of the Avengers. Clint is the son of Harold and Edith Barton and estranged younger brother to Barney Barton. Unknown to him, he is also the older twin brother to William Brandt, Chief Analyst and teammate of Ethan Hunt in Impossible Mission Force or IMF.

Howard Stark was an inventor, scientist, engineer, businessman and movie director. The founder of Stark Industries, Stark worked on various government projects during World War II, including the Manhattan Project and Project Rebirth, the latter of which resulted in using the Super Soldier Serum to create Captain America. Presenting Rogers with his vibranium shield, Stark aided him, as well as the U.S. Army and the Strategic Scientific Reserve, in the fight against HYDRA. He co-founded S.H.I.E.L.D. along with Carter to be the Strategic Scientific Reserve’s successor. Later in life, he married a woman named Maria and had a son, Tony. He co-developed the Arc Reactor with Anton Vanko and worked alongside Hank Pym during the Cold War.

Aaron Cross (born Kenneth James Kitsom) is an operative for the Department of Defense program Operation Outcome. He begins to question the program after accidentally killing civilians during a mission and eventually has to go on the run when Eric Byer tries to shut the program down and kill all of the agents.

Clinton Francis "Clint" Barton is an extremely skilled marksman, a former special agent of S.H.I.E.L.D. and one of the founding members of the Avengers. He is the mentor and, unknowingly, the biological father of Kate Bishop.

William Alexander Brandt is the deuteragonist of the 2011 film Mission: Impossible – Ghost Protocol and a member of Ethan Hunt’s team from the Impossible Mission Force. He recently reentered the field after learning that he wasn’t responsible for the believed death of Julia Meade-Hunt and reuniting with Ethan to take down Wistrom and Cobalt.