Phoenix Wing: Rettenjō

Phoenix: Rettenjō is a Nox Nyctores with the shape of a giant 55-inch nail.

Information
Rettenjō is an Anti-Nox-Nyctores weapon and severs ties with the Boundary. It was built by Konoe Mercury.

The core of Rettenjō is Kushinada's Lynchpin, which has the ability to stop the functionality of seithr, resulting in the rendered uselessness of Ars Armagus. Doing so, however, would cause the world's current order to be destroyed; as seithr is something that is used in everyday life, the world would be without a reliable power source, and Ars Magus would cease to exist.

Trinity Glassfille is the only person alive who knows its whereabouts, as it was believed to have been lost after the Dark War, when in all actuality, it was in Tenjō Amanohokosaka's possession. Before Tenjō's untimely demise at the hands of Jin Kisaragi, he gave Rettenjō to Bang Shishigami, who was unaware of its power.

Trivia

 * In one of the timelines, Rettenjō was taken from Bang by Relius.