In his blue challenger's room, Kai was revising his plans.
He had suffered terrible losses "thanks" to the black challenger's hands. Not that he cared about human lives, in fact, he was thankful Aito had ridden him of useless cannon fodders that would have betrayed him for gods at some point.
In a sense, he stood to benefit from the death of around a third of his sect members. Why? Because of the soul cores, he had harnessed from them.
Challengers' soul cores.
Those soul cores were of better quality than the ones found on the fourth and fifth floor. In general, a goblin's soul core was barely worth a third of a level 1 human and a hobgoblin's half.
The reason was unknown, but Kai had his own hypotheses. Either the Tower's monsters weren't as powerful as humans—clearly wrong—or simply because most challengers still alive had already absorbed quite a hefty amount of souls in their bodies.