Great War

Twenty Thousand Years Ago, the demons tried to destroy the world. Various races joined hands to repel the demons. It was said that the technology of ancient civilization was more advanced than the current technology in the current era. They have different powerful weapons and the people from ancient times knew how to create the Universal Grade Equipment. They also have connections to many different worlds. They used that force to pushed back the demons from the edges of the world.

That's the normal story of the Great War which was passed down through generations.

According to Cluster,

The demons were searching for something that's why they launched an invasion. They were looking for a door, an entrance to a different realm. It was because they said that the world, no, the whole cosmos was going to end soon. The Ieshi Clan also said that the world was going to end in the near future.

Of course, the other races didn't let the demons roamed in their territory, so they forced back the demons.

Then... Something entirely different appeared all of a sudden. It caused chaos in the whole cosmos. They thought that the end was coming, so the demons joined hands with other races. Cluster didn't have much information about this part, so her description was vague. But Souta understood that all the forces of the whole cosmos suffered great casualties. The Ieshi Clan disappeared, the Founding Gods of the God's Continent died, the Supreme Dragon God died, the Vajra race was annihilated, powerful leaders of Humans and Elves died, and also the progenitors of different monsters died.

According to Saya,

Monsters have contributed a lot in the war twenty thousand years ago. The progenitors and the monster lords showed their fearsome fight ability in that war. They defeated a lot of those unknown creatures who came out of nowhere.

They were always on the frontline showing off the power of the best feram. They were fearsome, fearless, and overwhelming that even scared the demis and humans at that time even though all of them were fighting the same unknown creatures.

No other race dared to take the role of the vanguards in the alliance of the cosmos except the monsters. Even those gods and deities felt fear of the power of the monster lords even though they were on the same side. Even a monster lord of the goblin race, slime, trolls, and orc contributed a lot in that war.

As long as a monster reached the evolution of the monster lord they will gain an overwhelming power that will put other races into shame. Unfortunately, most of the monster lord perished in that war along with the founding gods of God's continent and the deities of the Giza continent. Even the demon race suffered great casualties as several of their demon king and emperors died.

Souta Ieshi's findings,

He concluded that the era twenty thousand years ago was powerful and there were many gods and monster lords. But a great war occurred.

According to the legends, the forces of the Imperium fought the demon army. It was true but that's before the great war occurred. In truth, the opponents of Imperium were several times greater than the demon army.

She told him that the combined forces of gods, monster lords, spirit gods, and demon god were fighting something beyond this universe.

The invaders. He already guessed that these invaders came from beyond the door. The door must be some sort of transportation gate, dimensional hole, or teleportation gate that leads to another universe.

The great war must be the reason why the seven continents of Imperium were divided by great barriers.