The monsters that banded together have already started their march upwards Mount Olympus. They stayed outside the boundary of the foot of the mountain for a day before the monster commanders gave the order to climb. The Divine Realm Olympus stands on top of Mount Olympus as it is anchored to the mountain.
The Divine Realm Olympus is not the only divine realm that is like this when the world finally became bigger. Numerous divine realms have already started to assimilate unto the world which created the numerous factions of gods and divine beings. There were some that tried to forcefully assimilate but the world easily rejected them unlike what happened to Asgard. In the end, the gods and goddesses had to abide by the rules placed by the world to make sure that their divine realms can have a foot in the mortal realm.
