Temugin is the son of the Mandarin. Temugin had little contact with the outside world until he was delivered his father's rings and a note explaining that he must avenge his father's death at the hands of Iron Man.
He confronted Iron Man while the latter was investigating some illegal activity. He removed his rings to make things 'fair' and was able to severely damage the armor by attacking its 'stress points.'
Stark's countermeasures after their first encounter had limited success in their next fight. Temugin claimed that Stark's technology was a lifeless force and thus no match for the power of chi. Temugin prepared to deliver a finishing blow, but Stark revealed that the monk's order had become corrupt and were committing atrocities. This obviously clashed with Temugin's sense of honor. After their activities had been exposed by Iron Man, one of the monks literally stabbed Temugin in the back. He has sworn to avenge his father and make Iron Man pay. It is possible that Mandarin is using his son as a pawn or attempting to corrupt him in spite of his monastery upbringing.
Temugin was later recruited by Mister Lao, an agent of the Atlas Foundation, to be Jimmy Woo's second-in-command, fearing Woo was too soft for what the Foundation needed, and putting Temugin in place to succeed Woo as head of the Atlas Foundation.
Young Temugin became the step-son of Shin Zhang, the last man to hold the title Mandarin. Temugin changed his name to Gene Kahn after his mother mysteriously disappeared. It is heavily implied that Zhang had Temugin's mother killed, as he lusted after the power of the Makulan rings. When Zhang attempted to destroy Stark International, the plot is stopped by Iron Man. Zhang presumed that Obadiah Stane had unleashed this hero to prevent him from taking the Makluan ring, which he presumably didn't know its significance. Gene tried to convince Zhang to not to be so judgmental. However, Zhang refused to tolerate such insolence in front of his servants, The Tong, and warned Gene to be careful otherwise he'll join his mother.
Somehow, Gene managed to usurp Zhang as the Mandarin and forcibly took the second ring from Stane. He also had his first encounter with Iron Man. Gene discerned that the rings aren't a symbol of power, as Zhang thought, but as actually an expression of power itself, using highly advanced technology to perform such feats.
By chance, Gene befriended Tony Stark, who was secretly Iron Man, in order to find out the other rings location. Over time, the two of them, alongside Pepper and Rhodey researched the missing 3 rings, and tracked their locations. However, upon the conquest of the fifth ring, alongside finding out that Tony was Iron Man, Gene turned on his friends, revealing his alter-ego in the process. During this time, he almost killed Rhodey, and revealed the plane crash to Tony. However, he did appear to regret his actions, as shown by him teleporting the friends back to Rhodes' house, as well as a shot of him inside the temple, lamenting the good times. This does not last for long though, as it is revealed that he only wants the rings to do his mother proud, and does not feel worthy of them, until he chucks the rings at Fin Fang Foom, whom then reveals a map of the other 5 rings.
Gene now travels with Howard Stark, holding him hostage and using his knowledge to find the rings. Bits of their adventures appear in many episodes, though sometimes they are only glanced over, as they do not always cross paths with Iron Man. They recover the 8th ring together, but here Gene must also face off his stepfather.
Upon nearing the ninth ring Doctor Doom captures Gene and Howard. Gene must again seek Tony's help, and as a result, Howard escapes his grasp.
Gene eventually discovered the final Makluan temple in China, close to his old home. He wasted two days scouring the temple, finding himself walking around in circles. At the same time, he engages Iron Man, War Machine and Rescue (Pepper), who blast him through a wall, right into the ring chamber, where its guardian, a six-eyed bipedal lizard, awakens from stasis. The guardian introduces himself as an alien Makluan, the race that forged the ten rings from the beginning of time and had used to conquer the universe. However, he grew fed up with his race and stole the rings from the Makluan Overlord, seeking refuge on Earth, where he found Gene's ancestor, Khan, finding him noble enough to wield the rings after changing his DNA so he could utilize them. But as Khan grew old, he feared his children abusing the rings, so he hid them across the globe.
Gene demanded the last ring, but the Guardian said that his impure heart makes him unworthy. Refusing to accept that, Gene viciously attacked the guardian, eventually claiming the final ring. He attacks the Iron trio, but is briefly subdued by Howard, who had developed a quantum weapon to temporarily disable the Makluan rings. But Gene quickly recovered and vaporized Howard's weapon before fleeing.
The next day, on Tony's birthday no less, Gene appeared as the Mandarin and announced his intentions for world domination. SHIELD immediately responds to oppose him and Gene swiftly decimated entire squadrons before banishing the Helicarrier to the Negative Zone. As he faced off against Iron Man and friends, suddenly, a Makluan mothership appeared in the sky and teleported Gene aboard. The Makluan Overlord reclaimed the ten rings from Gene, leaving him powerless. Gene arrogantly declared that the rings are his and gloats about his defeat of the guardian. The Makluan Overlord reveals that the guardian was his son and revealed that he desired to revenge himself upon him for his treachery. The alien subjected Gene and Iron Man and friends to two matches in the Makluan arena solely to amuse himself. After they defeat the Berserker, the Makluan Overlord claimed they cheated and sent Iron Man and friends back to Earth, leaving Gene captive. As they watched Earth's heroes fight off the Makluan invasion, the Overlord tells Gene about his misguided intentions. Eventually, when the Makluan Overlord is defeated, Gene retakes the rings from him and uses them to teleport everyone on the ship to safety before it self-destructed. Gene then rescued the Helicarrier from the Negative Zone before declaring that he shall redeem himself by protecting the world, not conquer it.