Heroes 6 - Discussion

Angels are hierarchically higher than not just cavalry, but paladins, sacred warriors endowed with divine superpowers.
Perhaps angels don't walk on our land; maybe in the world of Heroes, people's faith in God is stronger.

I don't understand how, while justifying the place of devils in the Inferno race, one can doubt the existence of angels.

Well, there is some meaning to it, of course. In general, I would divide it like this:
Angels are the sky (I don't know what race that would be...).
Humans are the earth.
Demons are the underground realm of Hades.

It has always been the case that angels and demons are symbols of good and evil, respectively.
Humans are in the middle because they are a very controversial race. NWC tipped the scales towards good (I would even say towards holiness), and as a result, they were led by those who symbolize good, i.e., angels... This is perhaps the only real, not invented motivation that I find.

At the same time, the nature of angels, as celestial beings, is very different from most of those inhabiting the Castle...