Mortiis would be Norwegian, yes... Not that I've ever heard as much as a note he's sung, but
Phoenix Rizing, however, would be a great Norwegian band. Especially their cover of Aqua's "Roses Are Red"... I don't think I've laughted so much in years.
Yep, musically, at least, it's good to be Finnish (I wouldn't have the faintest idea of how it would be otherwise, but I suspect someone may soon tell me...

)
However, Norway's greatest contribution to music will forever be Edward Grieg.
If I was into Black Metal, I'd probably mention a lot of bands. But I'm not, so I won't. So there.
Worth mentioning that Satyricon actually mingled with the top spots on our top twenty, though... Nightwish peaked at 27 or something... Bah, at least it got up there.
If there were a country called Sweden, I might also mention the success Hammerfall has achieved there, but we all now that Sweden is just a bad dream and something mothers scare their children with.