Loken was one of the five Titan Watchers of Ulduar in the Warcraft series of computer games.
He served as one of Yogg-Saron's wardens, but was eventually manipulated by the God of Death's sanity-shattering powers. He eventually betrayed his brother, Thorim, and murdered his brother's wife, Sif.
Loken worked to free his master from its bonds, but this took time. He ordered the Iron Dwarves of Thor Modan to enslave the Earth Giants there and use them for his cause. This plan was foiled by the heroes of Azeroth, but Loken was not finished.
Eventually, the heroes made it the Storm Peaks, where the Titan city of Ulduar was located. Thorim was enraged by Loken's betrayal, and attempted to heal the wounds he inflicted on the Sons of Hodir so that they could work together to fight a common enemy. This worked in time, and Thorim and Loken had a final battle. Thorim was defeated and taken back to Ulduar as a prisoner and mind-slave of Yogg-Saron.
The heroes stormed the Halls of Lighting, Loken's personal sanctum. They battled his iron minions, and eventually battled Loken himself. Loken was killed, but a great light in the center of the room flashed on a map of Azeroth. Something was coming their way...
Months later, the heroes assaulted Ulduar once more and killed Yogg-Saron with the help of Thorim and the other three Watchers, Hodir, Freya, and Mimiron. Soon afterwards, they learned that Loken was "Azeroth's Prime Designate", meaning that if he was killed by Azeroth's heroes for any reason it would send a message to the Titans and tell them that something was wrong. The Titans send Algalon the Observer to inspect Azeroth in search for corruption - with the death of Loken, the corruption of a Dragon Aspect, and the corruption of another, percentage for planetary reorigination was 100%. Algalon battled the heroes, and learned that they loved life and were willing to fight for those he loved, so he rearranged the reply code, sparing Azeroth.