The Sigma-Circular: シグマサーキュラー http://i.imgur.com/VPNow89.jpg The Sigma Circular, or rather Sigma シグマ, is a destructive machine created by Banno and Roidmude 004 in order to dominate all of humanity. During the first attempt to activate this machine, Medic was originally meant to be a sacrificial vessel, but Brain takes her place to save her from brainwashing and sacrifices himself instead. Later, Gold Drive and the Reaper Legion infiltrated the Special Defense Center headquarters, and placed Sigma under evolution process before the Kamen Riders (and later joined by the now-defected Roidmude generals Heart and Medic) would stop him from his plan on occurring the second Global Freeze.
