Aldrich Killian was a budding, but crippled, scientist in 1999, heading up a fledgling think tank known as Advanced Idea Mechanics. Always on the lookout for sponsors to gain recognition for his group, he attended a New Year's Eve party in Bern, Switzerland, where he encountered Tony Stark. He approached Tony with a business proposition, but Tony brushed him off, lying that he'd meet Killian on the roof a short while later. Killian waited, but Tony never arrived, and over the next hour, he contemplated jumping from the roof to end his own life. Eventually, he resolved to stand up against the injustice of the situation and prove himself to the world without needing the likes of Tony.The experience of that night hardened Killian to the realities of life, and he quickly came around to the idea of acting as a facilitator, drawing fine scientific minds to himself instead of reaching out to others for support. Among his earliest recruits was Dr. Maya Hansen, a woman who had been spurned by Tony after a one night stand on that same night. Hansen brought her Extremis virus research with her into the folds of A.I.M. and Killian quickly grasped its potential in gaining lucrative military contracts.
After curing himself of his disability by using a dose of his own Extremis virus, he orchestrated many terrorist attacks as part of his experiments, while creating a false character known as "The Mandarin" through the use of an actor, to mask his illegal activities. He orchestrated the attack at Tony's home, kidnapping Pepper Potts afterwards. Having Pepper Potts as his "trophy" and hostage, he injected her with the Extremis virus to further motivate and antagonize Tony. After his men had abducted President Ellis, Killian had planned to orchestrate a live feed showing the murder of Ellis, only to have Tony and James Rhodes interrupt and attack their base with the help of Tony's J.A.R.V.I.S.-controlled Iron Man suits. In the ensuing battle, Tony finally found Pepper, only for her to be trapped under debris. Before he was able to rescue her, an angry Killian attacked Tony. Tony managed to distract Killian so as to allow him to rescue Pepper.
While Pepper seemingly died after falling to her apparent death, Killian approached Tony and taunted him for a one-on-one battle. The two engaged in a brutal fight with Tony switching between various Iron Man suits as Killian destroyed each one after another. As Tony was unable to attach any more extra armor onto himself, JARVIS sent the Mark 42 prototype to aid Tony in his battle. Tony then kinetically attached the armor onto Killian to stall his movements. After commanding the suit to pin Killian against the wall, Tony then activated the Mark 42's self-destruct function, thus blowing Killian up in the process. After the scaffolding in which the two were fighting was destroyed, the battered Tony is confronted by Killian who is shown as surviving the explosion. Taunting Tony, he elaborated upon the revelation that he is the true culprit and that he is in fact "The Mandarin" and that the two should stop hiding behind "false faces". Just before he is able to attack Tony, Pepper attacked him from behind, having survived her fall with the help of her new found Extremis abilities. Just before Killian was able to retaliate, Pepper knocked him away. After ripping an arm off from one of the stray Iron Man suits, Pepper attached it to her herself and utilized its capabilities to finish off Killian for good.
