Kusari no Ten

Kusari no Ten (天の鎖; lit. Chain of the Heavens) is a vaguely described sort of barrier created by a race of deities. Anyone possessing the status of the Kusari no Ten is often referred to as being Realm-Bound. The Kusari no Ten was specifically designed towards the Shinraifu, them being the most powerful of all Realm-Bound beings, and prevented them from ascending to higher planes of reality, with the realm of Heaven being their limits. According to legend, this restriction was though to have played a major part, or at least have been a significant factor, in the mysterious and sudden disappearance of the entire Shinraifu race.