I have no idea if the term sludge thrash exists, but for lack of better, that's what I'll use to describe the unusual output from the Danish combo Unbelief.

The output of the Danes really does have its own sound and feel. It's not death metal, eventhough there are definitely elements of it. Pure thrash it isn't either. It has a sludge feel, no doubt. An almost lazy sound, but hard and heavy.

Definitely a band to check out if you like extreme metal with more than just raw power.