I believe there is a demon realm, perhaps a dimension accessible via rinnegan, where the various demonic summonable entities originate from.
The hierarchy is as follows.
The King of Hell resides over this realm, those with the Rinnegan can summon it to the mortal world, he commands life and death as well as whether souls become demons or pass onto the pure world. As seen when he is summoned by the Rinnegan (in the manga), he is surrounded by black flames, this is because those flames are the flames of hell and are summoned forth with the mangekyo sharingan.
Under the King of Hell are the Shinigami, who assist in the punishment and sealing of evil souls.
Other demonic entities that reside in this dimension include demonic ogres like the ones summoned by Tayuya as well as chakra devouring astral worms. The seeds which create Shinju trees also come from here, thus explaining why those with the ocular powers from the tree have abilities associate with this dimension.
The hierarchy is as follows.
The King of Hell resides over this realm, those with the Rinnegan can summon it to the mortal world, he commands life and death as well as whether souls become demons or pass onto the pure world. As seen when he is summoned by the Rinnegan (in the manga), he is surrounded by black flames, this is because those flames are the flames of hell and are summoned forth with the mangekyo sharingan.
Under the King of Hell are the Shinigami, who assist in the punishment and sealing of evil souls.
Other demonic entities that reside in this dimension include demonic ogres like the ones summoned by Tayuya as well as chakra devouring astral worms. The seeds which create Shinju trees also come from here, thus explaining why those with the ocular powers from the tree have abilities associate with this dimension.
