Requirements met: Evolving Blood Manipulation!
The lower the level and the lower the Order of the existence, the more benefits one would receive if by chance of destiny, luck, or by real skill, succeeded in defeating and killing a higher level existence of a higher Order.
The clearest example was the effect and the amount of Soul Power absorbed. Back then, when Bai Zemin faced a First Order existence for the first time, he went directly from level 15 to level 20 with a single step. The same thing happened recently when he killed the Second Order Surprisingly Strong Archaic Bear; just one kill sent him from level 40 to level 45, apart from acquiring a lot of additional stats as a reward.
Bai Zemin had made a wild and rough estimate just based on his experience so far and deduced that to rise from level 40 to 45, he would have to have killed hundreds of thousands or even millions of enemies or at least a hundred to two hundred First Order creatures.