Necromancy

Necromancy (死霊術 (ネクロマンシー)) is a type of magic that is manipulates the dead, and is grouped alongside Hopping Zombie Spell, Hand of Glory, and Vetala Sorcery.

Background
The word "necromancy" is adapted from Late Latin necromantia, itself borrowed from post-Classical Greek νεκρομαντεία (nekromanteía), a compound of Ancient Greek νεκρός (nekrós), "dead body", and μαντεία (manteía), "prophecy or divination." As the name suggests, necromancy is the magic of manipulation of the dead for communication for the purpose of divination.

It is unknown what its true form is in the Toaru Majutsu no Index universe, but it can be assumed that is related to the spirits of the dead, in referenced to its kanju.

Kazakiri Hyouka Arc

 * Main article:Kazakiri Hyouka Arc

It is after Index sees Kazakiri Hyouka's leg regenerate completely after kicking Sherry Cromwell's golem down, and saving her.