With the extinction of the human race drawing near, the four kings of the ancient empires—the King of the East, South, West, and North—finally stepped forward.
With the aid of the Divine Beasts under their control, they faced the monsters threatening humanity.
The beasts drew their power directly from the towers. If their strength were to be assessed, they would be classified in a realm beyond SSS-Rank.
A mythical rank.
The kings took on the SSS-Rank and SS-Rank monsters, while the remaining forces dealt with the weaker creatures.
What followed was a devastating battle.
A battle that would last for twenty years.
By the end of those twenty years, Earth's population had been reduced by seventy percent.
But the kings were also paying a terrible price.
The immense power they had been exerting far exceeded what their mortal bodies could withstand. Their bodies began to deteriorate under the strain, and they knew they could no longer continue fighting.
With humanity still in danger, the kings transferred the marks of their Divine Beasts to their successors.
And so, the next generation inherited the responsibility of protecting humanity.
The aftermath of the twenty-year battle was a devastating blow to Earth.
The land had become barren, and most of the seas had been drained. The Earth, once filled with abundant resources, wildlife, and fertile land for cultivation, had been left in ruins.
The immense outbursts of mana and the shockwaves caused by the monsters rampaging across the planet had affected every living creature. Even the animals that had survived were changed, while much of the land itself had become barren and infertile.
Fortunately, the old kings had stockpiled resources throughout their lifetimes. These reserves were used to support the surviving population and help humanity endure the difficult years that followed.
The people also began working to revitalize the world, finding ways to make the barren lands usable once again.
Eventually, they discovered a method of safely consuming the monsters that inhabited the seas. The oceans had become the only remaining source of abundant wildlife, although nearly all of the creatures within them were now monsters.
From time to time, surviving land animals were discovered. Whenever one was found, it was captured and placed under protection so that it could be bred and help restore the world's wildlife population.
Two years later, the economy had finally begun to recover, and civilization was once again moving in the right direction.
Then came the day everyone had been waiting for.
The official ceremony for the new kings was held.
The new kings ordered that 100 knights be sent into the towers every year, with the goal of preventing another disaster like the one that had nearly wiped out humanity.
Two years later, the knights had conquered 50/100 floors of the tower.
As a result, they were granted permission to leave the tower.
It was a year of celebration and joy. Humanity could finally enter and exit the towers at will.
But on the 5th of July, A.O., a World Announcement suddenly appeared.
[WARNING! WARNING! WARNING!]
TOWER ENERGY HAS BEEN DEPLETED.
ENERGY REQUIRED TO MAINTAIN EARTH'S PROTECTION: INSUFFICIENT.
TIME REMAINING UNTIL THE DOME COLLAPSES: 1 HOUR.
[TOWER CLOSURE PROTOCOL ACTIVATED]
THE TOWERS WILL BE SEALED AFTER THE DOME COLLAPSES.
UNAUTHORIZED BEINGS ARE ATTEMPTING TO BREACH EARTH.
ALL REMAINING ENERGY WILL BE REDIRECTED TOWARD DEFENDING THE TOWERS.
THE TOWERS CAN ONLY BE PROTECTED FOR AN ADDITIONAL 2 YEARS.
After the announcement, many people were left with puzzled expressions. They had no idea what the dome mentioned in the message was.
As far as they knew, there had never been a dome covering Earth. Whenever they looked toward the sky, all they saw was the vast expanse above them.
But the kings and the older nobles knew the truth.
A new threat was coming.
And it was far greater than the Dungeon Outbreak.
The kings were faced with a difficult decision.
Should they fight the approaching threat, or hide within the towers and wait for their inevitable deaths?
The old Southern King finally proposed an idea.
"Right now, I believe the forces attempting to break through aren't that numerous. The fact that the dome hasn't collapsed yet proves that they haven't succeeded.
But if we hide inside the towers and wait for them to break through, they will have time to bring in more forces. At that point, our only options will be to surrender or fight a battle we are destined to lose.
But if we strike now, while their numbers are still limited, we still have a chance of winning."
The other kings agreed with his proposal.
They immediately began preparing for war.
The women and children were evacuated into the towers, along with all the remaining resources that humanity possessed.
Meanwhile, the men and young boys remained behind.
They stood together, prepared to fight to the death.