[alexti]

That's a hard task to find something matching particularly well. In most cases either theme or music or lyrics don't match. So far I've found only the following:

Pangaea - Korpiklaani (korpiklaani=woods clan), whole album Spirit of the Forest fits well, if one song,probably With Trees

Marignon - Agalloch - Kneel to The Cross

Vanheim - Bathory - Blood On Ice - "The Revenge Of Blood On Ice"

Ulm should probably be something heavy, but nothing seems to suit in particular, the best I can think of is Warlock's "True as Steel".

Somebody suggested Megadeth for Ermor which seems fitting, though many black/doom metal bands would fit too. I've thought about Pentitent's "Into the Great Inferno" and "Entering the Gate" which have very different sound, but probably suit better.

For other nations I don't even have a clue what would fit really well...