Ladon and his sister Dahlia were born in the mining country and as children, conscripted to Cowen's service while at the rank of Computers Third Class. For Ladon, growing up in the Genii bunker was very frightening for him due to having lived in the mining country before and he had nightmares for years afterwards. Dahlia kept Ladon from waking the barracks they grew up in and raised him. As they grew, Ladon and Dahlia tutored each other in each new thing they learned so that they rose together through the ranks of the Genii. (SGA: "Legacy: Homecoming")
Formerly Cowen's chief scientist, he was included in Commander Acastus Kolya's strike team against Atlantis. Radim quickly got the hang of the Lantean technology including the sensors which he used to guide the teams after Major John Sheppard. When Kolya requested reinforcements, he was knocked unconscious by Sheppard who raised the Stargate shield, killing 55 men. Later, he was one of the few able to evacuate through the Stargate. (SGA: "The Storm", "The Eye")
After the failure of the Atlantis mission, Commander Acastus Kolya began plotting to overthrow Cowen and took Radim into his confidence. Radim, feeling that neither Cowen or Kolya was qualified to lead the Genii, betrayed Kolya's information to Cowen, forcing him to go underground, while beginning to plot against Cowen. This was motivated by the fact that his beloved sister was dying and he felt he had nothing left to lose. In an elaborate triple cross, he offered a Zero Point Module (which was depleted) to the Atlantis expedition, in exchange for supplies for his "rebellion" against Cowen. Ladon's sister Dahlia Radim and a team went to get the supplies, while Lt. Colonel John Sheppard and Dr. Rodney McKay went to get the ZPM. Sheppard, McKay, and a group of soldiers were captured by Cowen, who thought that Ladon was still working for him. Cowen demanded the expedition's Puddle Jumpers, and revealed that Dahlia and the others of her team were dying from radiation poisoning. Ladon intended to detonate the Genii A-bomb killing the soldiers and Cowen, but when he learned that they could save his sister's life, he freed them, allowing the weapon to go off and kill Cowen. He then returned to the Genii homeworld and assumed power. After the coup, Ladon chose Dahlia as his Chief Scientist, both because of her level of skill and because of their close bond. He also felt greatly indebted to Atlantis for saving her, a debt he felt he could never repay or even dare to try to repay. (SGA: "Coup D'etat", "Legacy: Homecoming")
When Commander Acastus Kolya heard of this, he felt that Radim had stolen what was rightfully his. He captured Lt. Colonel John Sheppard, using a captive Wraith to feed on him, demanding Ladon in return. Dr. Rodney McKay and Ronon Dex were willing to turn Ladon over, but Ladon eventually discovered the Stargate address that they were being held in. (SGA: "Common Ground")
When some of the Lanteans aboard the Tria came back to reclaim the Atlantis and relocated the Athosians to New Athos, he asked Teyla Emmagan and Ronon Dex to join him and the Genii in their fight against the Wraith. (SGA: "The Return, Part 1")
When Atlantis returns to Pegasus, Ladon is informed of the development by his Chief of Staff Ambrus and warns Sora Tyrus to not engage Atlantis or do anything to antagonize them, knowing of her grudge against Teyla Emmagan. Ladon threatens to dismiss Sora from his service and reminds her that attacking Atlantis had not worked out well for him. Ladon also hopes that Atlantis' return will buy them time to finish a new project and possibly to enlist Atlantis' help in it.
After foiling an attempted coup, Ladon is enraged to learn that Sora attacked a medical relief mission and stole supplies from Atlantis. While Ladon recognizes the desperate need the Genii had for the supplies, he chooses to return them rather than antagonize Atlantis further. He informs the expedition that he'd had Sora stripped of her rank and arrested and will put her on trial. Teyla later suggests that Ladon only didn't execute her because of how popular her father had been. Ladon and Woolsey then enter negotiations with each other to resume relations and Sheppard notes that both Ladon and Woolsey clearly enjoy it.
After Guide warns them of a coming attack on Levanna, the Levannans contact Ladon and the Genii for help. Through a three-way connection, Ladon admits that his spy network has picked up a couple of whispers about Levanna, but it could be because General Safren Valless, the leader of Levanna is building up their technology so much. However, Woolsey and Ladon worry that the attack on Levanna could be a feint to draw attention away from somewhere else, but Ladon agrees to send a machine gun squadron led by Colonel Faber to assist in Levanna's defense and supplies the Levannans with more weapons. Woolsey realizes from the way Ladon does it that his intelligence suggests that the main attack will in fact happen at Levanna and is positioning it so that the Tau'ri will take the blame if something goes wrong and not the Genii. (SGA: "Legacy: Homecoming")
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