Ok, they're black metal and I'm sure everyone knows them, but I think 
Enslaved's later albums have an occult influence, albeit one that's usually not very overt. It's done in a more intellectual manner than the majority though. The same could be said for Negura Bunget/Dordeduh, but as I only have second-hand desriptions and google translate versions of their lyrics I'm not sure.
The Finns might be aware of both of these, but 
Hexvessel are a great retro-folk band. Their cover of 
Diamonds by Paul Simon adds another dimension to an already great song.
And finally as this is the English forum 

, more people outside of Finland should be aware of 
Mana Mana. I've only read translations of a few of their songs, but some seem to fit an occult description. Their second album is more musically accomplished, but as Jouni Mömmö had died by this point the vocals just don't have the same resonance.
'Oh Krishna, restless and overpowering, this mind is overwhelmingly strong; I think we might as easily gain control over the wind as over this.'