Steles
No one knew exactly when the Celestial City would depart, nor when the end of the world would occur. It could be a week, a month or a century from now. His Main Mission didn't include a time frame, but the Race Against Time theme was a clear indication that he'd better get his ass in gear.
Anyone who moved to the Celestial City too soon would have to fend off the relentless onslaught of millions of desperate migrants. No matter how strong they were, if the oncoming waves of attacks continued unabated for too long, the best warriors would eventually succumb from exhaustion.
This planet was huge. Champions and monsters at the top of the power ladder must have been tens, if not hundreds of thousands. Those considered mighty enough to become local tyrants, but not quite powerful enough to dominate the world, probably numbered in the millions.