Every time the demon race invades, intense battles occur at the borders between the Outer Realm and various Divine Kingdoms. These battles cause the Outer Realm seals to continuously break and become difficult to repair!
But, focusing their attack on the Seventh Divine Nation is different.
If during their invasion of the Seventh Divine Nation and the Lingwu Continent, the other Divine Nations completely sever their connections with the Seventh Divine Nation, exiling it along with the Lingwu Continent to the Outer Realm, and successfully repair the Outer Realm seals, then it would be extremely difficult for them to invade the other Divine Nations again!
By that time, it would take countless years to wear down the Outer Realm seals before another invasion could occur again...
Of course, if the Divine Nations really do this, it would mean sacrificing countless lives in the Seventh Divine Nation and the Lingwu Continent in exchange for the safety of the other Divine Nations...
