Activation index

The Index is an object found on every Halo. It is the figurative key needed to activate the "installation", causing a reaction that will purge the galaxy of sentient life. This removal of all sentient life is to starve the The Flood, who cannot be defeated otherwise. It is roughly T-shaped, with a faint blue-green glow emanating from a stripe on each side. Halo cannot be activated unless the Index is inserted into the control panel in Halo's control room. The "Sacred Icon" is first seen in Halo: Combat Evolved where (with the help of 343 Guilty Spark) the Master Chief locates and attempts to activate the Halo, but he is stopped just before turning the key by Cortana. Cortana then begins to argue with Guilty Spark over the index. After the Master Chief breaks up their fight, Cortana explained to him the true function of Halo. (Previously Guilty Spark had implied that it would only destroy the Flood.) The Index of Installation 04 was last known to be in the possession of Cortana.

The The Covenant High Prophets regard the Index as a Sacred Icon.

Similarities between the Index and other Artifacts

It should be noted that the Index bears a marked resemblance to depictions of Mjollnir, Thor's hammer. Several other parallels might also be drawn between the two Sacred Icons, especially when one combines the purpose of the Indices, and their respective Installation 04:

• Without his hammer, Thor loses the ability to control thunder and lightning.
  • Indexes are the means of control for activating the Installations.
• Mjolner is "the most fearsome weapon" of the Norse gods.
  • The Indexes give the bearer control of the most devastating weapon of the Forerunners.
• Traditional Norse belief was that it also symbolized both the destruction and regeneration of life.
  • The Forerunners' intent was that the destruction of life in the Milky Way Galaxy would destroy The Flood. Only after the Flood was destroyed could life begin again.

Another odd tie between the two is the creation stories of Mjolnir.

• One story tells us that Mjolnir was the product of Loki's trickery, smithed at his request; similarly, 343 Guilty Spark beseeches the Master Chief to unite the Index and Halo's Core, effectively replaying the role of Loki.
• Another story says that Mjolnir "descended to Earth as a meteorite"; It is theorized at this time that The Ark, the only other means of activating Halo units, crashed or landed somewhere on Earth. This belief is thought to be confirmed during the Halo 3 trailer Bungie released; it has a massive structure arising from the ashes of New Mombasa. See the Halo 3 article.

The tie between the two icons is, at best, speculation. However, in support of this argument, it is a matter of record that Bungie, the studio which produced Halo, often uses strong religious nomenclature, or the names of legendary weapons (they also have a history of self-referencial Easter eggs and the use of the number seven). Several examples have been cited:

1. The name of Gandalf's sword, Glamdring, translates to Foe Hammer, a Pelican dropship pilot from the first Halo game.
2. The name of the Master Chief's Armor is Mjolnir Marks V (in the first) and VI (in the second). If we accept the rumor that Halo is to be a trilogy, that would make the final model (assuming his armor is upgraded before the conclusion of the game) Mjolnir Mark VII (seven). The tie between this "most fearsome weapon" and the Forerunners' Indices and Halos is purely speculation within this article, but provides another interesting tie between the Master Chief, and the original Reclaimer.
3. The Brute's Chieftan, Tartarus, is named after the "worst Hell" of the Greeks.
4. Cortana is named for Curtana, the legendary sword of Edward the Confessor.
5. The tie between the main character of the Marathon game and John 117 (Master Chief before Mjolnir armor) have been liberally discussed. If this is held to be true, then Marathon enlists the help of John, a cyborg supersoldier, much as the marathon which Pheidippides ran from Athens to Greece enlisted the help of the Spartans in war.
6. The Covenant name for the remote activation site of the Halo weapon system is The Ark. This may be a reference to the Judo-Christian Ark of the Covenant.
7. In the Marathon game, the name of the rampant AI is Durandal, another legendary sword.

More to that point, if we retain the belief that the Chief Security Officer character is John 117, then a sword which is purported to have belonged to Hector of Troy, is destroyed by a Spartan, as the city of Troy was destroyed by spartans during the Trojan War.

There are many such recorded ties to significant artifacts, people, and places of mythos, within the universe(s) of Bungie fiction; it is likely (though, again, speculative) that the tie between the appearance and purpose of the Index, and Mjolnir are not coincidental.