It's the legendary polearm of Odin in Norse mythology. In the world of ToAru Majutsu no Index it is the spiritual item desired by Magic God Othinus in order for her to remake the world. Many magic side events surrounding the first half of Shinyaku ToAru Majutsu no Index is related in some way in acquiring a requirement in its construction. Othinus later indeed acquires the spear, and uses it to destroy the world before the eyes of Kamijou Touma.
