Magano

Magano is an alternate world with the appearance of a barren land and ruins of buildings. impurities live in Magano and can travel to the human world through gaps in the limit between the two.

Exorcists are able to travel to and leave Magano with a special talisman. In the manga, only powerful exorcists are allowed to do so, as it's a very dangerous place full of Impurities. If weaker exorcists were to be killed in Magano, their powers could be absorbed by impurities, strengthening them.