List of references to Norse mythology in Halo
From Halopedia, the Halo wiki
In the Halo Universe there are several references to Norse mythology, or simply the Norse people. Below are a few of them.
Loki; Loki was an AI on Harvest who shifted shape when changing his role with Mack. Loki, in Norse mythology, was the god of chaos, mischief and treachery, and could shift shape. Additionally, he was also infamously known to be a trickster - much like Mack. The Pillars of Loki was also a nickname for a training course on Reach.
Sif: Sif was the shipping operations AI on Harvest. In Norse Mythology, Sif was the wife of Thor and the goddess of wheat and fertility. In Norse mythology, Loki stole Sif's hair. Harvest's space elevator strands, controlled by Sif, were compared to her "hair" in Halo: Contact Harvest. Near the end of the First Battle of Harvest, Loki destroyed the Tiara with a mass driver, bringing the seven space elevators down on the planet.
Jotun: Jotuns were human farming machines. Mythologically, they were giants.
Fenrir: Fireteam Fenrir is a team of Spartan-IVs and also a variant of the MJOLNIR [GEN2] armor. In Norse mythology, Fenrir is a monstrous wolf and Loki's son, destined to slay Odin and in turn be slain by Tyr.
Utgard: Utgard was the capital of Harvest. In Norse mythology, Utgard was the stronghold of the giants.
Bifrost: Bifrost was a bridge that connected Midgard and Asgard.
Vigrond: Vigrond Highlands was a place near Utgard on Harvest. In Norse mythology, it is the plains where Ragnarok is said to take place.
Ida: Ida is named after the plains in Asgard.
The Index: The Activation Index is supposedly similar looking to Thor's Hammer.
GUNGNIR: Project GUNGNIR is named after Gungnir, the spear used by Odin, the Norse god of war. The symbol for the project is also fashioned after the symbol for the mythological Gungnir. The GUNGNIR helmet has one "eye", as did Odin.
Skidbladnir: The colony ship UNSC Skidbladnir is named after the ship made by Loki to fit all the Gods. Loki was also the shipboard AI of the Skibladnir before it was made Harvest's Planetary Security Intelligence.
MJOLNIR: The MJOLNIR Powered Assault Armor, that is designed specifically for the SPARTAN-II's, is also the hammer of Thor. Mjölnir translates simply to "crusher", referring to the hammer's pulverizing effect. The hammer was also able to shoot bolts of lightning. Mjölnir is only able to be wielded by Thor through his iron gloves, Járngreipr, and his belt megingjörð. In a similar fashion, only the augmented Spartans are strong enough to wear the armor.
Berserk: Sometimes a Brute goes on a rampage nicknamed "berserking". The Norse had warriors, called Berserkers, who were followers of the cult of Odin (the one-eyed Norse god of war) and believed in the importance of a warrior dying heroically in battle rather than shamefully in his bed. They were said to have been immune to pain and possess uncontrollable aggression, and fought wearing only bear or wolf skins, entering a trance-like state before battle. When berserkers went into their battle state of mind, they tended to lose their sense of reason, mercilessly attacking and killing anything in the way of their weapons. The berserker's behavior seems to come from ingestion of drugs such as alcohol before combat, although that would make them difficult to use on the battlefield, similar to the Brutes from Halo 2 as well as Halo 3.
Ragnarök: Ragnarok is a map of Halo 4. In Norse mythology, Ragnarok was a series of future events, including a great battle foretold to ultimately result in the death of a number of major figures, the occurrence of various natural disasters, and the subsequent submersion of the world in water. Afterward, the world would resurface anew and fertile, the surviving and returning gods would meet, and the world would be repopulated by two human survivors.
Sedra: The colony world of Sedra is noted by Lieutenant Michael Horrigan as "still [believing] in Valhalla." Colonel Randall Aiken, formerly Randall-037, also makes several references to the Norse Hall, telling Jameson Locke more than once that "They don't let ONI into Valhalla"; "They" assumedly being the Æsir.