- "My death... heralds the end of this world."
Loken was one of the Titan watchers tasked by the Pantheon to watch over Azeroth in their absence. Elevated to the role of prime designate, Loken was the chief jailor of the Old God Yogg-Saron, imprisoned in the depths of Ulduar. However, the whispers of the Death God eventually drove Loken to betray his comrades and bring down the works of the Pantheon. With Ulduar and the Forge of Wills under his control, Loken created an army of iron constructs, such as the iron dwarves that battle the earthen throughout Northrend.
According to the Tribunal of Ages in Ulduar's Halls of Stone, Loken — also known by various sources as "Keeper Loken", "Sentinel Loken", "Kronus", and "prime designate" — was named the supreme protector of Azeroth by the Pantheon, leading the aesir (storm giants) and vanir (earth giants) following the containment of the Old Gods. Along with his brother Thorim, the Stormlord, as well as Watchers Hodir, Freya, Mimir and Tyr, Loken was designated as a guardian to watch over the prison of Yogg-Saron, deep within Ulduar. Over time, however, Loken succumbed to the whispers of the Old God and turned on his allies, taking control of Ulduar and seeking to unravel the plans of his former masters. At some point he provoked a global war to break out between the storm giants and earth giants, which was ended by Loken "neutralizing" them. After the conclusion of that war, Loken placed the earthen, giants, and vrykul into stasis at designated holding facilities (presumably, facilities like Uldaman or Ulduar).
Among his other acts of treachery was the murder of Sif, the wife of his brother Thorim. Loken tricked Thorim into believing that it had been the work of Arngrim, the king of the ice giants, turning Thorim against his allies. Much later on, Thorim — having realized he'd been had — gathered his weapons and armor (with the aid of players) and confronted Loken in combat. However, being so far from his sanctuary in the Temple of Storms allowed Loken, in proximity to his dark master, to overpower his brother.
Loken was presumably the Watcher of the Temple of Wisdom; he can be found in the throne of the Temple during the confrontation with Thorim in  .
Links to Ulduar
As prime designate, Loken's task was to protect the world of Azeroth and subsequently act as chief jailor of the imprisoned Yogg-Saron. After his corruption, Loken subdued the other watchers, facilitating Yogg-Saron's possible escape.
Once in control of Ulduar, Loken utilized the services of Ignis the Furnace Master on at least two occasions. One was the transformation of Veranus, Thorim's proto-drake, into the plated monstrosity Razorscale. Loken also ordered the construction of Kologarn, the massive stone construct, to guard the Shattered Walkway that leads into the inner halls of Ulduar.
When he is killed in the Halls of Lightning, Loken says that his death "heralds the end of this world", after which the map of Azeroth bursts into fire and launches a beacon of light toward the sky. According to the Archivum Console in Ulduar, the "Algalon failsafe" - an automatic emergency signal following the death of the prime designate - was activated immediately following Loken's demise, resulting in the arrival of Algalon the Observer. The console goes on to explain:
- "Destruction of prime designate is considered the first warning sign of systemic planetary failure. Algalon Observer entity's arrival is followed by planetary diagnostics resulting in one of two possible reply signals. Reply code Alpha: signaling all is well, and Reply code Omega: signaling planetary re-origination."
When asked to explain "re-origination", the Console replies:
- "The decomposition of the planet and its living organisms into base elements: metals, rocks, gases. This is followed by a period of reconstitution of each element into the original planetary blueprint."
In other words, the Titans would destroy all of Azeroth and everything on it, then rebuild it from the raw materials left behind from that destruction - thus giving credence to the dire warning in Loken's dying breath.
Loken is also involved in the following quests:
Encounter in Howling Fjord
- Come, minions! Your master calls!
- The work of your brothers in the Storm Peaks has reached a frenzied pace. Soon, Father will be freed.
- Your brothers to the north have subjugated the stone behemoths and set them on the path to Ulduar. Soon, the remaining defenses of the Pantheon will be neutralized.
- The three fissures opened by the mortals of this region must be silenced. The earth hears and sees what we do and will continue to interfere with our efforts if the way is not closed.
- Bury this place, your master demands it!
Encounter in Grizzly Hills
- You're late, overseer.
- Destiny will not wait. Your craftsmen must increase their production of the war golems before the stone giant leader and his army reach Ulduar.
- Tell your rune-smiths to continue converting what stone giants you can. Those that will not submit must be destroyed.
- If the stone giants interfere with our work at Ulduar, I will hold you and your thane responsible. Mortals must not be allowed to come to the aid of the giants.
- Return to your duties, overseer. Be certain to impress upon your workers the urgency of their tasks.
Encounter in Halls of Lightning
See Loken - Quotes
Loken's name is most likely based on Loki, the main trickster of Norse mythology. With Angrboda, he was the father of Fenrir, Jormungandr, and Hel. Although Loki is actually a Giant, he is a blood brother of Odin, and Odin, Thor and Loki are featured in many stories in Norse mythology. However, Loki turns on the Aesir when he tricks blind Hod into killing Baldr, setting off the events that would lead to Ragnarök (Apocalypse, End Of The World). At Ragnarök, Loki would lead the giants and inglorious dead into battle against the Aesir and the Einherjar (glorious dead), and there he would do battle with Heimdall, the watchmen of the gods, and both would slay each other. Interestingly, it's Loken's death that causes events in WoW to spiral out of control leading to the possible destruction of Azeroth.
Loken is also referred to as Kronus by the earthen from Ulduar, and a few other quests, which is a reference to Cronus, the first Titan of Greek mythology and father of several deities of the Greek pantheon. This may be an alternate name or a leftover from the Alpha, before his name was finalized.