Iron Legion

The Iron Legion was created after the events of The Avengers. After Tony Stark's near death experience and battle with the Chitauri and Loki Laufeyson, he realized that Iron Man couldn't do it all on his own, and the world couldn't always count always on The Avengers, that he needed an Iron Legion.

Iron Man 3 Prelude
After New York, Tony Stark began building an Iron Legion and expanded it to no limit.

Iron Man 3
Tony Stark was working on the Mark XLII, which was going to be the next member of the Iron Legion. Even though he has 41 other suits, most are more weaponized and advanced, he still uses the Mark VII. After his house was destroyed and the President was kidnapped, Tony ordered the "House Party Protocol", which activated all the Iron Man Armors back at what remained of his house. They then met up with him on a oil rig just as they needed back up in Florida, where The Mandarin planned to kill the President on live TV. Tony ordered the suits to attack all Extremis soldiers and "take them to church," which they did.

Hammerhead dove right into a group of Extremis soldiers. Bones then split itself to its basic components and hit several soldiers, sending them falling to their deaths and recombined. Meanwhile the Extremis soldiers rip off Hammerhead's head and arms, causing it to fly and spin out of control, crashing into the oil rig. The rig would have fallen, but Igor lifted it back up. The battle continued between the Extremis soldiers and the suits. Red Snapper was covered in Extremis soldiers, so Tony ordered Heartbreaker to help him out. Heartbreaker killed all but one Extremis soldier, who ripped off his face, sending Snapper into the oil rig, making a huge explosion and trapping Pepper Potts. Silver Centurion then came onto Tony and Heartbreaker picked up Rhodey and the two flew off to find Pepper. However, a Extremis soldier jumped onto Heartbreaker, forcing it to let Rhodey go.

Two Extremis soldiers were about to attack him, but Thumper came and smashed the ground, sending them flying. He then punched them into the air and Tank shot them. Tony then found Pepper, but Killian came and overheated Silver Centurion, thus making it useless. Meanwhile, two Extremis soldiers try throwing steel bars at a Tiger, which blasted them. A Extremis soldier tries to jump onto Tony but a suit attacks him. Tony called for another suit, which Bones came to respond, however, just as Tony was about to jump into it, another soldier jumped onto Bones and attacked it.

Rhodey rescued the President and left with the Iron Patriot, letting the Iron Legion finish the job. After Pepper fell into the fire, Tony put on Nightclub and fought the Mandarin, who ripped off the suits arm and punched right through it, but Tony ejected himself into Shot Gun. After a brief fight on the roof, Killian sliced the suit in half, but Tony again ejected out in time. Just as he is about to kill Tony, the Mark XLII comes to the fight, however it hits a pole and separates. Tony wraps it around Killian and self destructs it. Tony then jumps off and part of another Iron Man suit comes and just saves Tony, but crashes to the ground. Killian then reveals that he survived and is about to attack Tony, claiming himself to be The Mandarin, when the Pepper, who survived because of the Extremis added to her, comes and smacks him away with a pole. The Mark X then comes and mistakes Pepper for a Extremis soldier and blast her. Tony tells it that she is not a target, but his communicator was knocked away. Pepper then punches through the suit and uses it's Repulsors to kill The Mandarin once and for all. J.A.R.V.I.S. then reports that all Extremis soldiers are terminated and Tony orders the "Clean Slate protocol" which self destructs all remaining suits.

Trivia

 * The Mark VII armor may have been in the Iron Legion as it was in use at the time of their construction.
 * The Wine Cellar they are kept in was built by Igor.
 * In the promotional poster, Nightclub, Heartbreaker, Tank, Silver Centurion, Bones, Shot Gun, and the Mark XLII can be seen.
 * In the promotional items, the Heartbreaker, Thumper, Silver Centurion, Bones, Igor, Shot Gun, Hammerhead, Peacemaker, Red Snapper, Gemini and Mark XLII were the most used Armors.
 * Despite Gemini's high profile, it had nearly no screen time in Iron Man 3.
 * Igor may still be functioning, as if he was destroyed the rig would have collapsed.
 * Only twenty one suits were shown exploding during the "Clean Slate Protocol", two are shown to be destroyed by Extremis soldiers, the Mark X was smashed by Pepper, Igor held up the oil rig, and four suits were destroyed by the Mandarin. Six others are missing, presumably destroyed by the Extremis soldiers during the battle.
 * In the movie, only Hammerhead, Bones, Igor, Heartbreaker, Red Snapper, Thumper, Silver Centurion, Nightclub, Shotgun, and the Mark XLII are seen doing something in the battle, although you can barley see Tank, Tiger, and Piston fighting briefly.
 * Marks I-VII are seen in the Iron Legion page of the Official film tie-in.
 * War Machine, Mark V, Mark III and Mark VI are seen with others in a photo of the Iron Legion.
 * One of the original names was the Iron Avengers.
 * It is unknown if Hot Rod, a War Machine prototype, was actually at the Extremis battle because Tony says that all the armors are only "coded to him."