The ancient battlefield was a battlefield where the aliens clashed against humanity in the past. Countless humans and aliens had perished here, and some aliens had been imprisoned in the battlefield as slaves. The battlefield itself was turned into a training ground for humanity.

Many of the surviving aliens were still incomparably powerful. After spending years in recovery and giving birth to mutated descendants, they had created their own homes in the battlefield. They had also gathered many of the remains of the battlefield, hoping to one day break the seals imposed upon them by the humans and leave.

The humans had entered the battlefield once again, and the aliens definitely...