Board Thread:Theories and Rumors/@comment-25684301-20160215135802/@comment-4013721-20160216152014

the realms are based on balance, light and dark, good and evil. Thats how the hole sister realms works. The Cursed Realm is the dark, evil counterpart to Djinjago which is the good, light counterpart to the Cursed Realm.

So really thats how the realms must be working. The reason i think that is because the ghosts and the djins all uses the same ghost tail peice.