Wolves in the Throne room is a good example of a band. Amon Amarth as well. I also like Bal-Sagoth. Old In Flames.
I don't mind dark. Anything based of of H.P. Lovecraft is dark...and probably not in the way Diacide is dark. I know there's plenty of Secular bands out there that rip and are thought provoking.
No christian bands though.