The only issue I have with the circus idea is that its an animal, and a rather dominant one at that.
A species that common wouldn't be found strictly at a circus, or anything like that.
All the other beasts are found in their own ecosystem, so why wouldn't Blacephalon be apart of a forest, or something?
They're predatory, and their dex entries make them out to be stealthy hunters.
In order for that to work, the terrain would have to be very bright, and loud.
I like what
>>34849779 said, but that brings up the question:
What do you think their life-cycle is like?