Atmospheric BM/Blackened Folk. Yes, I chose two, and while here can be some melody differences (IE the folk element) there's a huge amount of bleed-over. I get a very similar vibe off both that I just lump it all together. Drudkh, Fyrnask, Dordeduh, Negura Bunget, Agalloch, Burzum, Blut Aus Nord, Moonsorrow, Wodensthrone, Spectral Lore, Wolves in the Throne Room, Falkenbach, Myrkgrav, Primordial, Walknut.
It tends to root out the overly goofy elements from folk, while toning down the "trying too hard to be evil" elements of orthodox BM. You're just left with well written heavy dark music that sets a great tone.