Nigon is the second underground race.

Arandor's very first words in this thread:

Let me warn you right away!!! There's no need to write: "Why a second Dungeon?" The developers said that the Stronghold is the last expansion, and so on! People who say that should go chop wood in the forest)))

And you write:

A second Dungeon? Why?

So go chop wood in the forest))) But no offense! ;)
And in general, in my opinion, it's already been broken that each race has its own opponent. Nowhere in the story were dwarves enemies of orcs, and they live almost at opposite ends of the world of Ashan, if you look at the map. So, in my opinion, a dwarf is not an enemy of an orc. Moreover, there was a period of time between the release of Hammers of Fate and Tribes of the East when there was an odd number of races.