Mokkerkalfe

The Mokkerkalfe or Mökkurkalfe (モックルカールヴィ) is a prefabricated giant made out of clay from Norse mythology, to assist Hrungnir in his battle against Thor.

In the world of Toaru Majutsu no Index the legend is used as a basis for at least two spells.

Etymology
was a giant made out of clay to assist in his battle against. It was an artificial life form that was made from a mare’s heart contained within a giant mountain-like body of clay. The legend said the mare was so cowardly that Mökkurkalfe could not fight properly and Thor’s servant destroyed it.

Mokkerkalfe of Buckingham Palace
Prior to the Battle of Buckingham Palace, Kamijou Touma, Index, and Villian, third princess of the British Royal Family, go to its underground tunnels directly under it in order to destroy a barrier that would allow them to access a branching railroad track needed for their battle against Carissa. The magic barrier is of course the Mokkerkalfe. It is actually a spiritual item based on the creation of Mokkerkalfe, made to protect the subway tunnel and the special railway car for Curtana Original. According to Index, it was designed to fight against Thor who was was known for having top-class strength even among the Norse gods, but the story goes that, at the very, very end, the wrong material was used for the ‘heart’, which led to poor results (most likely a reference to it being afraid of Thor at the mere sight of him). Here, it was apparently optimized as a custom model made to protect the location they were in (the hidden tunnel) by rethinking the materials from the ground up using British theories, and the heart was used as a symbol for "warning".

Appearance and abilities
It is initially in the form of a wall where it was used to hide the branching tunnel, and had the same color and texture of the surrounding walls. The "wall" was furthermore hidden by a large poster. When it is discovered, pale beams of light shoot from the center of the wallpaper across the height and width of the tunnel wall. Then in an instant, a grid of rectangles with the exact same size as the "poster" begin spreading out. The "wall" begin to undulate, and then each of the square portions of the grid flip up like posters, tear off, and form aggregation of paper. Then, after spiraling around like a storm it them concentrates into one spot, taking the form of a giant made out of paper.

The strength of the paper giant's fist was described as being able to "easily turn a car to scrap in a single strike," and its gait was huge for it had large legs, and a great distance it can cover in a single step. Its body was described as being as hard as stone. Since it is magic, it is vulnerable to the Imagine Breaker, Touma's right hand. However, it cannot wholly be negated. When Touma touched its fist, a wire-frame made up of paper crumpled to form strings where the outline of its fist used to be. The paper giant compensated for this loss by turning its right hand into a sharp stake. Moreover, it can remove parts of itself if there is a need to, like when its arm was stuck to a wall.

Like Sherry Cromwell's Golem, the Mokkerkalfe paper giant is susceptible to Index's Spell Intercept. Finally, it is also primarily susceptible to a spell done by someone of royal blood, at which point, it will slowly crumble. In Villian's case, she used a Notarikon, as suggested by Index, to quickly chant her spell, in essence a "Quick Spell".

The chant: " () In accordance with the order of one who has inherited the proper blood, open quickly!O A G P A T A C O T P O T R B! "

Mokkerkalfe of GREMLIN
Seemingly closer to the original myth, GREMLIN, the magic cabal primarily known for its magicians whose basis are from Norse mythology, utilizes Mokkerkalfe as well. Here, it is deployed for the GREMLIN invasion of Tokyo in order to intercept enemies coming closer that may interrupt Majin Othinus' attempt at creating Gungnir.

Here it is referred to as being "a mountain-like giant made of dried clay," and is large enough to alter the ley lines. It wades upon the waters near Tokyo, and is able to easily walk upon the ocean floor, rising 500 meters above the ocean surface.

It's core was a "heart on a plate," which was kept on the Sargasso near Tokyo Bay, the current base of operations of GREMLIN. It was a dark red heart, and as oppose to the legend of using a mare's heart, it is apparently a heart that was made from a much more powerful item, though it is unknown what it was made of. Regardless, despite being in the open and upon a plate, it was strong enough to keep on beating like a proper heart. The heart is set up to control Mokkerkalfe remotely. As it is its core, the Mokkerkalfe will crumble if it is destroyed, as exemplified by Ollerus, under the guise of Thor, crushing it in his hands.

According to Othinus, this Mokkerkalfe is Freyja's territory, a fellow member of the group, though it is unknown how she came to have such a powerful spell in her possession.