Jigoku

Jigoku is the Realm of Evil. It is a realm of pure, darkest evil and the source of the oni and the Shadowlands. In that dark place to the south of [{Rokugan]], the veil between Jigoku and Ningen-do is all too thin. Though all of the Spirit Realms are occassionally referred to as "Jigoku", the proper use of the name is only for the one dark Realm. (F&W p. 6)