Beast Wave

A beast wave is a natural occuring phenomenon that appears once the beasts population increases enough so that the beasts can't find enough food, so they invade other territories to obtain food and if possible increase they're territory, until the condition happen again.

Given the nature of beasts, once there are enough Hundred Beast Kingg, Thousand Beast Kings, and Myriad Beast Kings will appear, even a Mutated Beast might appear, but the conditions are hard to achieved. After all without a territory that can birth enough of the three categories of beast kings a Mutated Beast will not emerge, even if the right amount of time is spent in a territory that can only birth a limited number of Myriad Beast Kings.

There are some Myriad Beast Kings can be compared to Mutated Beast in the danger area as long as a mutated version of the latter emerges. Such as the Lightning Lycan King! It might appear inferior to a normal Myriad Beast King but it has the same level of intelligence as humans, thus mutated Myriad Beast King can be considered as an existence at the rank of a half-a-step Mutated Beast. Don't forget that there is a wide margin between between a true Mutated Beast and one that is comparable as one only in danger terms even though both are comparable to rank 5 Gu Masters, thus the name of half a step Mutated Beast.

After all Qing Mao Mountain could only create three Myriad Beast Kings existences, and the appearance of a single Lightning Lycan King is rare, thus if in a medium the rate of variated Myriad Beast Kings is very far in between the generations, the chances of a Mutated Beast appearing is literally 0.

Thus the more Myriad Beast Kings there are the higher the chances of a variations of said Beast King to emerge at the time of the beast wave and automatically the higher the chances for them to appear more often when Myriad Beast Kings emerge. When those conditions of land, beast kings existences and time are satisfied than literally one Mutated Beast might appear, and the more variations of Myriad Beast Kings there are plus the normal ones than at least two Mutated Beasts will appear.