Demon Prince
Ashton's adventure in the Outside World taught him many things. He had learned a lot of things that he would otherwise never learned had he remained inside the protective bubble of the Last Bastion.
One of those things is the fact that Humanity never really had an idea about the upper limits of what the foreign races can grow into...
It's a common language that the strength of Demons is based on their 'maturity' represented by the number of horns they have as well as their bloodline. Angels on the other hand based their strength on how many pairs of wings they have and how big their halos were.
For demons, a pair of horns represents Infants, 2 pairs are Teenagers, 3 pairs would be Young Adults, 4 pairs are Adults, 5 pairs are Elders, and 6 pairs ars Ancestors.
At least, this is what most humans believed in the entirety of it. That's wrong though.