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.

Lance of Gungnir Arc
He appears before the Knight Leader, William Orwell, and second princess Carrisa after the initial bomb bombardment of Sargasso and introduces himself to them. He comments that Othinus gave him the task of protecting this place with his life before his explanation is cut short by being shot through the throat with an arrow fired via a Robin Hood spell. Loki then fell from the tip of the tanker he was standing on and slammed into the ground. Carrisa then ordered all of them 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): 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.