The Blessing

Gods and Demons used to walk among mortals on the physical plane, their war carried out across both planes.  
The Gods took mortals under their protection, gave them gifts and protected them from the cruel ministrations of the Demons.  Demons on the other hand used mortals as instruments against the Gods, or for slaves, or even for food, both physical nourishment as well as a source to boost their magic.  
Gods believed mortals to be a charge, something to protect and teach, even if it was often as a lesser being, like a pet.  Demons believed mortals were lesser beings and therefor to be used however they saw fit, like cattle for resources and that mortals had no need to be treated well since they were so much less than Demons.
This on going conflict consumed the world of Rit and the Gods came to believe that the only way to truly protect the mortals of Rit was to separate the moral and immortal realms, trapping the Demons in the immortal realm and leaving the Gods to be able to move back and forth between the two.  

A great magic shall we perform, protection for the mortals our war has injured more than any other. We shall combine our power and perform a miracle the likes of which has not been seen since the time of the first battle between Demons and Gods.

- Lord Ceitus

God of Knowledge and Light

To the Conference of the Faithful, 2 days before the Blessing

On the day now known as the Hour of Blessing, all of the Gods gathered at the former stronghold of Bexxa'wyld, on the top level of the tallest tower to weave their great spell.  A small host of Gods rode out against the Demons to distract them from the great magic to be performed.  The Gods cast their minds into the void and created the desired magic, but something went wrong.  Something interfered with the spell and the world was split, part of it still accessible to Demons, but none of it being accessible to Gods as they were all banished to the immortal plane.  Many Demons and Gods died that day, as did many mortals. By the end of the day, the world had been remade, the Demon Lands remained where Demons walked still on the mortal plane and the rest of the world was free of Demons and no Demon could step foot on, nor fly over, or burrow under the lands now known as the Blessing.  
Many turns passed until mortals were able to recover, returning to some level of civilization.  Cities lay in ruins.  The former residences of Gods fell to ruin or were buried in the earthquakes that followed the Blessing.  
The Demons made effort after effort in the beginning to breach the barrier, but their very nature denied them access beyond the borders of the Demon Lands.  This didn't preclude them sending Devils and Monsters against the mortals in the Blessing, but the creation of such for them only be destroyed by the mortals in the Blessing cost precious magic resources and even that eventually stopped.
The efforts have now changed to subterfuge, sneaking, and the appeal to the baser instincts of mortals, like greed, fear, cowardice and hubris.  It has not provided a way yet for the Demons to reach the Gods to continue their war, nor access to the mortals in the Blessing.

Type

Metaphysical, Divine