Brísingamen

The Brísingamen (ブリーシンガメン) is the spiritual item used by the Gremlin (Norse) magician Freyja to "give birth" to a variety of creatures based on figures from Norse mythology. Although, based on the legendary, the torc or necklace of the goddess , the spiritual item extends to all the jewels connected to it.

Etymology
The word Brísingamen or Brísinga men is an Old Norse compound, whose second element is men "(ornamental) neck-ring (of precious metal), torc". The etymology of the first element is uncertain. It has been derived from Old Norse brísingr, a poetic term for "fire" mentioned in the anonymous versified word-lists (þulur) appended to many manuscripts of the Prose Edda, making Brísingamen "gleaming torc", "sunny torc", or the like. However, Brísingr can also be an ethnonym, in which case Brísinga men is "torque of the Brísings"; the Old English parallel in supports this derivation, though who the Brísings (Old Norse Brísingar) may have been remains unknown.

Appearance
Despite being derived from the legendary necklace or torc, the spiritual item is instead a long golden chain where several types of jewels are inserted into. It has not been shown at all to have ever been worn as a necklace, instead Freyja keeps it in her mother's pockets.

Principles
According to Freyja, that is the fetus that controls the body of her mother, she uses a Brísingamen jewel as the core and then guides her magic power through her mother's womb to give it a specific directionality of germination, allowing for her to choose which creature would form once a Brísingamen jewel is used. She then pours that magic power into a Brísingamen jewel, which she can apparently use anytime she chooses.

Usage
When used for the first time, Freyja mutters the words: "Come forth, Brísingamen." At which point, the sound of a hard object is heard and a glowing jewel appears in Freyja's grasp. She then says a unique chant, and at which point red thread appears and quickly wraps itself around the jewel to form the creature. Freyja apparently has no limit on how many creatures she can form, and can as well summon same type of creature even after one has already been summoned. An exception to this is Níðhöggr, where she summoned two and the second one Vol. 02 appended on its name. The summons are immune to pain, but can still be destroyed. Gravity and the laws of physics still affect the creatures, as such they can lose balance when a part of them is destroyed, or can crush metal if they are large enough. All of them are vulnerable to Kamijou Touma's Imagine Breaker, and are destroyed instantly upon contact. Of Brísingamen itself, Touma conjectures that he too can destroy it with a touch.

When summoned Freyja can give them commands, or like Níðhöggr can act independently by giving instructions on what to do even if Freyja is no longer in control of it.

When she "gives birth" to a creature, she utters a unique chant dependent on a few parameters written in such a manner: Cost [Parameter 1]. [Parameter 2]. [Parameter 3] / / [Parameter 4]
 * The first parameter just after Cost, refers to a number. It is unknown what the number indicates but it can be assumed to be either the jewel she used, or the creature she has summoned.
 * The second parameter refers to the Color she will use for her summon, which is either black or white. If Freyja's explanation below on how she has "black (black)" and "white (good)" or evil devour each other, it can be assumed the colors correspond to the role Freyja gave to the summon, either good (white) or evil (black). Presumably through this set up, only white creatures can eat black creatures, (as exemplified by Hildisvíni eating Þrymr summons) and vice-versa.
 * The third parameter refers to either Call or Shift. The Call mode most likely refers to summoning a creature, while "Shift" mode has an already summoned creature become larger. When using the latter mode the creature chosen eats its fellow creatures taking also their jewels, and Freyja would then indicate the "Cost" for it, the number of which refers to how many of the creatures the chosen creature can consume. Norse mythology is a mythology of mutual destruction, where the gods and their enemies were set up from the beginning to die fighting each other she can construct a spell that accentuates that fact. Her spell can create an attack attack that allows good and evil, white and black to devour each other.
 * The fourth parameter refers to the name of the creature or being based from Norse mythology she wants to summon.

List of summons

 * All summons are based on creatures or beings from Norse mythology.

Concept Art
According to Haimura, all of Freyja's "children" are made solely from an outer skin that is knit like a sweater, so they are hollow inside like a balloon or airship.