In the First Gate, claiming territories did not just mean "capture the flag." It was a situation where one had to face manifestations of monsters generated by the territory itself, fighting them off until one achieved victory.
This part was usually relatively easy for various universes as there was no requirement to send only one person, like what Dante or Portia did. Most universes either sent over a group of qualified fighters or simply relied on technology to achieve their purposes.
As Levi had stated, unclaimed territories before one activated the flag/spire were the same. The type of monster created varied, but their average strength was basically the same throughout the First Gate.
Though, one eerie fact that Levi did not mention was that somehow, and strangely enough, the standard of strength for these monsters was based on pure humans, not from the Eternal universes, but all universes as a whole.
