Sacred Haven of Debauchery

However, I am generally a staunch opponent of such factions in games, as using such obvious villains so easily ruins any plot.

The main antagonists in the sixth part were angels. And also in the third part of Disciples, since we are talking about it.

Because it's some kind of incomprehensible, ugly mess of ugliness.

The problem with the demons in the sixth game, in my opinion, is not their ugliness, but how generic they look. In the sixth game, they took common fantasy images that are used everywhere and didn't bring anything particularly new. Moreover, they even managed to make a couple of units look very similar to each other.

At least some of them had a style in the fifth game.

Imps and pit lords were good, but the rest are not impressive either. Although, at least the faction didn't look like a uniform red mess.