Norse Mythology

Norse Mythology (北欧神話) is the mythology of the North Germanic people around the time of the Viking Age (at its height covering most of northern Europe, much of modern Germany and Austria, and parts of the British Isles), continuing through into modern-day Scandinavian folklore, and following the lives of the Norse gods — the Æsir and the Vanir — and the men whose lives they directly affected.

In Toaru Majutsu no Index, Norse mythology is often used as a base for Magic. Its prevalence in its usage as a basis for magic is second only to Christianity.

Etymology
It is important to note that the correct appellation is Norse Mythology, not Viking Mythology. Originally, the word "viking" meant the act of faring overseas and the sailor participating, while in English it denotes a profession meaning something like "pirate". Only a minority of Norsemen were Vikings.

Principles
Like most traditional polytheistic systems, it has no set canon and in some ways resembles a body of customary beliefs more than a set religion. It has been speculated that only chieftains and other wealthy people held faith in the Æsir, while the common farmers believed in land-spirits such as dwarves, trolls and giants.

It is a branch of the Proto-Indo-European mythological tradition, which also spawned the Celtic, Greek, and Vedic pantheons; it's distinguished from those myths, however, by the fact that its gods are not only fallible, but also all mortal. They could, and did, die, as exemplified during Ragnarok, the Norse version of the apocalypse, which ends with most of the gods dead.

Many texts describing Norse beliefs have come down to us, but, aside from a few runic inscriptions and similar fragments, all were written hundreds of years after the turn to Christianity. Consequently it's nearly impossible to tell which stories are "Christianized", or how much they are, although academic theories abound. Even ignoring this, another problem arises: since Norse myth has no definitive canon, the myths differ considerably from place to place, according to the time they were written and the purpose they were written for.

Norse Mythology being a polytheistic religion, its gods had emotions that are very much alike those of humans. When the opinions of all the many gods were gathered, it created a single flexible system. As long as that system ultimately led them down the right path, everything was fine. As the gods of Norse Mythology are not absolute, the gods reach perfect answers when combined in a single group by complementing each other's weaknesses, creating a sturdy defense system. Moreover, an intrinsic property of Norse Mythology is that it is a mythology of mutual destruction, set up from the beginning so that over 99% of gods and their enemies would die fighting each other (likely a reference to Ragnarok). As such, a magician can create a countermeasure against a spell that uses figures from Norse Mythology if they made use of the figure that killed the other figure in the mythology.

History
It is implied that the legends surrounding Odin is derived from the Magic God Othinus herself or that Norse mythology, apparently among other religions, was influenced by her existence, such as the religion shifting from one centered around a hammer-wielding lightning god to a lance-wielding god of war, a god of magic sacrificing his own body by hanging himself from an ash tree to fulfill a contract, and Odin being a muscular one-eyed man with beard. It is implied that Othinus may have deliberately took different forms that eventually found its way into the mythology.

As a pagan religion, it is likely that Norse religion was also affected by the onslaught of Christianity and had their old gods either referred to as fairies or classified as demons.

Toaru Majutsu no Index SS2
During this collection of sidestories, Kanzaki Kaori encounters a Valkyrie known as the Jeans Slasher, and Ollerus makes his first appearance.

British Royal Family Arc
The group New Light, which made use of Norse-based magic, was involved in transporting the Curtana Original in the lead up to Carissa's coup d’etat. Moreover, the Knight Leader incorporates Norse Mythological aspects into his spiritual item Hrunting as well as a defensive spell known as Thororm's Defense Formula. A defensive spiritual item based on Mokkerkalfe at Buckingham Palace also appeared.

Toaru Majutsu no Index: Stiyl SS
The conflict in this sidestory was over several artifacts which were believed to have held the secrets of the Dvergr's skills. The main antagonist, Richard Brave used Magic based on the flaming sword Lævateinn.

Toaru Majutsu no Index: Kanzaki SS
During the events of this sidestory, Kanzaki Kaori fought a variety of adversaries who made use of Magic based on Norse mythology, culminating in a battle with the Valkyrie Brunhild Eiktobel who sought to complete Gungnir.

Shinyaku Toaru Majutsu no Index
A large part of Shinyaku Toaru Majutsu no Index consists of the protagonists' struggles against the Norse-based cabal GREMLIN.

Other

 * Asgard: One of the Nine Worlds supported by Yggdrasil and the home of the Aesir.
 * Asgard is mentioned by Othinus as one of the Phases which have been applied to the world due to various religions, Norse mythology included.
 * Bifröst: The rainbow bridge which connects Midgard (the human realm) and Asgard (the realm of the gods).
 * Orlentz Trice named his base after Bifrost.
 * Seiðr: A type of magic that is primarily used by female Norse magicians.
 * New Light uses this type of magic to create a certain type of song which causes one to see an illusion while it is being used, but also has a spell that can remove its ‘intoxication’. This spell works with both illusions that trick the brain and illusions that directly cause an image to appear.
 * Ragnarök: The twilight of the gods, a series of events in the future, including the death of Baldr, the harsh winter Fimbulvetr and various natural disasters, culminating in a great battle between the gods and their enemies, resulting in the deaths of most major Norse figures and the submersion of the world in water. Afterwards, the world will resurface from the sea anew, the surviving gods will reunite and two human survivors will repopulate the world.
 * Not referenced in itself in the story but is referred to in conjunction with other terms and figures from Norse Mythology whose importance is related to Ragnarök.
 * Runes: A set of letters forming an alphabet, believed to have been given by Odin. Odin acquired them by being hanged from Yggdrasil for nine days and nights.
 * Many magicians use Runes, created through various means, for their Magic.
 * The significance of the number Nine: The number Nine is a significant number in Norse mythology. For example, there are nine worlds supported by Yggdrasil and in order to obtain wisdom, Odin was hanged from Yggdrasil for nine days and nine nights by his own spear.
 * The Jeans Slasher makes use of the significance of the number Nine in her Nine Support spell.
 * Yggdrasil: A giant sacred ash tree, also known as the World Tree, which supports the Nine Worlds of the Norse cosmos.
 * Yggdrasil is referenced in the name of the magic cabal Those Who Prevent the Extermination of the World Tree.

Norse-based Organizations

 * GREMLIN (magic cabal)
 * Those Who Prevent the Extermination of the World Tree (magic cabal, destroyed)
 * Iron Stake that Carves Knowledge (magic cabal, destroyed)
 * Champions from the Sea (magic cabal, destroyed)
 * Those who Know the Rune of the God’s Sword (magic cabal, destroyed)
 * Hammer that Tempers Gold within the Earth (magic cabal, destroyed)
 * New Light (cabal reserve army)