Bab 1601: No Fun For The Wicked.

He found the seal quickly. It was at the center of the divine plane. It is equidistant from the realm rift, so no matter the direction he comes from, he will need to travel the same distance to reach it. But he will only find it if he moves in a straight line in its direction. Any other way, and he will go around in circles. 

No one attacked him on the way, so he had to lament, "The Tyrant race is smart and powerful, but they have lost the power of diversity." 

Apart from the fact that the Tyrant realm doesn't have different races to strengthen their defense against the demons, there are also no gods in the divine plane to fight the demon gods and keep them here. A single divine plane was able to keep CARNAGE from invading a plane in the High Heaven Realm, so the importance of gods is clear.