Iron Man's Iron Legion is a team of mechanical suited heroes that fought in lieu of Iron Man when Tony Stark was put out of commission. In Iron Man #300, the villainous Ultimo manages to return and beat down Tony Stark. Stark survives, but he is put into a completely comatose state. This allowed Ultimo to speed off to tear through California. The only person standing in Ultimo's path was War Machine, but he knew he wasn't enough.
However, James Rhodes had a plan. He'd bring together a team of heroes to don a series of Tony Stark's older Iron Man suits. With them all wearing them, they'd manage to work together to defeat Ultimo once and for all. While the Iron Legion managed to overcome Ultimo briefly, the villain wasn't subdued until after Tony Stark emerged from his comatose state to put the rampaging fiend down for good.
The Iron Legion briefly appeared in the Marvel Cinematic Universe as a series of robotic suits first controlled by Jarvis, then later overtaken by Ultron. However, in the comics, each suit had its own host. In order, here's the name of every member of the Iron Legion, why Rhodes chose them, and what happened to them during the fight.
War Machine
The founder of the team is James Rhodes, better known to comic readers as War Machine. When leading the Iron Legion, War Machine wore his classic War Machine Armor -- also known as the Iron Man Suit Model 11. Rhodes has been Tony's confidant for years, sometimes taking up the mantle as Iron Man in the past. It seemed reasonable that, when Tony was indisposed, he'd help bring the team back full force. However, who he selected to join the Iron Legion might be of interest.
Eddie March
Eddie March might not be a name familiar to fans of the films, but in the comics, he's a boxing friend of Happy Hogan and an employee of Tony Stark. Hogan hooked Eddie up with a job with Tony. Eddie was one of the first people to take up the mantle from Iron Man, with Iron Man briefly considering handing the title of Iron Man over to Eddie. Eddie donned the Iron Man Armor Model 1 in the Iron Legion, more commonly known as the classic grey armor. While Eddie put up a great fight against Ultimo, he was ultimately beaten.
Happy Hogan
Another familiar name to fans of the Marvel Cinematic Universe, Happy Hogan is Tony Stark's chauffeur and bodyguard. Being a former boxer, Hogan was always a capable fighter. As a member of the Iron Legion, however, he proved to be a worthy fighter. However, he ultimately was ordered by War Machine to bring Carl Walker and Eddie March, both defeated at that point by Ultimo, to a hospital. He proved most valuable as the chauffeur to those who needed to move -- fast. Hogan donned the Iron Man Armor Model 2, also known as the Proto-Classic Armor Tony's first upgrade to his Iron Man suit and the first suit to incorporate advanced technology and color.
Carl Walker
The other member of the team who Hogan had to carry away, Carl Walker, formerly known as Clayton Wilson, briefly worked for Justin Hammer, having earned the criminal's attention after donning his own mechanical armor. Known as Force, he eventually turned to the side of justice thanks to his hero, Iron Man. Walker would ultimately have a rocky relationship with Tony, since it was Hammer's stolen Stark tech that he incorporated into his Force armor. Walker would don the Iron Man armor before joining the Iron Legion, where he wielded the Iron Man Armor Model 4 -- also known as the Classic Armor. Carl was beaten when the armor began melting.
Mike O'Brien
Michael O'Brien was an NYPD officer turned a member of Project P.E.G.A.S.U.S. and head of security at the Vault Supervillain Prison, O'Brien initially believed Tony responsible for the death of his brother. Ultimately, it took multiple confrontations before O'Brien was convinced of Iron Man's moral integrity. O'Brien donned the Iron Man Armor Model 8, more commonly known as the Silver Centaurian Armor. Eventually, War Machine told him to evacuate nearby cities once it seemed as though any hope of stopping Ultimo had been lost.
Bethany Cabe
The only woman in the Iron Legion, Bethany Cabe is a former employee of Stark Industries and former fling of Tony Stark. She had an affair with Tony while married to her husband, who she falsely believed to be dead. Eventually, her husband was murdered following a series of complicated events. She was eventually called out of retirement to take on the mantle of Iron Woman, donning the Iron Man Armor Model 9, Neo-Classical Armor. She ignored Rhodes's direct orders to abandon ship, fighting until the end alongside War Machine until Tony Stark returned to fight Ultimo.