Celestial Spirit World

Celestial Spirit World(星霊界) is the place where all Celestial Spirits spend their time when not called through by their summoners. Being in the World seems to have some sort of rejuvenating effect on the spirits, restoring their health after being in the human world which, over long periods of time, can potentially kill the spirit. The reverse is also possible: humans are unable to breathe in their World so after a period of time, albeit a much shorter one, they would die. Such an occurrence (a human entering the Celestial World) is a serious breach of contract. This rule, however, is not absolute, since Natsu survives an extremely brief period in the Celestial Spirit World when he catches hold of Virgo just as she transits through the spirit world to reappear elsewhere in the human world at Duke Everlue's command.