Loki

Loki (ロキ) is a character introduced in Shinyaku Toaru Majutsu no Index. He is a member of GREMLIN, who is used as bait against the Anti-GREMLIN Alliance in their assault on the Sargasso of the North Sea.

Etymology
In Norse mythology,, is a God or  (or both) and is the companion of Thor. Loki's relation with the gods varies by source. Loki sometimes assists the gods and sometimes causes problems for them. Loki is a shape shifter and in separate incidents he appears in the form of a salmon, mare, seal, a fly, and possibly an elderly woman. He should not be confused with Útgarða-Loki who is named for the a different, his name literally means "Loki of the Outyards" to distinguish him from Loki.

Appearance
He was described as an old soldier holding a cane and wearing a silk hat and tailcoat that look like an illusionist or a stage performer.

Personality
Although having a high respect for Othinus, calling her Lady Othinus, he still bears the name of Loki, and though despite given orders from her not to worry about traitors, he continued to doubt his comrades, and made it so to fool both his comrades and the "traitor" for the sake of their mission.

Background
Doubting his comrades, he formed a dome surrounding the real Sargasso base of GREMLIN in Tokyo Bay in order to fool the traitor he believed in their midst. The celestial bodies in the dome corresponds to the coordinates in the Sargasso in the North Sea, and there, Loki waited for those who have fallen for his ruse.

Lance of Gungnir Arc
He appears before the Knight Leader, William Orwell, and second princess Carissa after the initial bombardment of Sargasso and introduces himself to them. He comments that "Lady Othinus" gave him the task of protecting the Sargasso of the North Sea with his life. His explanation is cut short however, after he is shot through the throat with an arrow fired via the Robin Hood spell. Loki then fell from the tip of the tanker he was standing on and slammed to the ground. Carissa then ordered all of her men to continue moving forward.

Loki suddenly rises, explaining that he is just an illusion and the real Loki is no where near the area. He explains that he was suspicious of his teammates and worried about a spy, so he created an artificial sky over Sargasso and altered Marian Slingeneyer's notes. Carrisa and the others then realize they have been led to a false Sargasso on the other side of the world. The illusion bids them farewell and disappears, just as the place is bombed.

Territory of Víðópnir
Territory of Víðópnir (ヴィゾヴニルのお膝元) is based on (Old Norse, possibly "wide-open" or "wind-weaver") is a rooster that sits at the top of Mímameiðr, a tree often taken to be identical or another name for the World Tree Yggdrasil. The spell creates a dome around a certain area that displays celestial objects on it like a planetarium. Loki used it on the true base of GREMLIN to fool the intruder he believed have infiltrated their midst.

Other magic
Loki can apparently make a fake body using a doll made cut of out wooden board. It mimics the appearance of his body completely, allowing to even seem injured. He also apparently has a power to completely "swallow up" or destroy a small island like a Sargasso one, using an explosion.