Loken had an affair with Sif, the wife of his brother Thorim.
Yogg-Saron, from his prison within Ulduar, muddled Loken's thoughts and made him lash out at Sif, scared at the thought of losing her, and he killed her by accident. Horrified at what he had done but too scared to tell Thorim the truth, Loken tricked Thorim into believing that it had been the work of Arngrim, the king of the ice giants, turning Thorim against his allies. Loken would stop the war between Thorim's and Arngrim's forces with an army he had created with the Forge of Wills,
but unknown to Loken Yogg-Saron had planted the curse of flesh inside the forge, which would slowly convert titan-forged into flesh and could also spread to those forged before the curse was created.[3]
After Thorim retreated to the Temple of Storms in despair, Loken was desperate to cover his actions, even if it meant using Yogg-Saron's power to do so, for if Algalon or the Pantheon ever found out his life would be forfeit. He arranged the death of Mimiron, making it look like a lab accident, though Mimiron's mechagnome followers would create a new mechagnome body to house the Keeper's soul.
Loken subdued Hodir and Freya, corrupting them into complacency with Yogg-Saron. He convinced the titan-forged Helya to imprison Odyn, the Prime Designate, within his Halls of Valor, claiming the title of Prime Designate that was rightfully Odyn's in the process. Loken expected Ra to come up from the south and investigate what was going on, but Ra never arrived. This is because he had discovered that the Pantheon was dead, killed by Sargeras, and had locked himself up in the Mogu'shan Vaults in despair. Afterward, Loken exiled all titan-forged from Ulduar and retreated into the depths of the complex.[3]
The final two Keepers were Tyr and Archaedas, who had seen what Loken did to the others and left before he could reach them, alongside their friend the giantess Ironaya and the earthen, mechagnomes, and vrykul of the Storm Peaks.
Tyr and his allies stole the Discs of Norgannon, which record all history in the world,[3] to investigate the extent of Loken's betrayal. Discovering the theft, Loken sent horrific monsters called C'Thraxxi after Tyr's group, but Tyr sacrificed his life to fight the creatures while his comrades escaped with the discs