Black Cobra's music falls under the rubric of sludge metal, and the aptly titled Invernal is their fourth full-length release. While sludge metal is prototypically slow, heavy and lumbering and rich in blues-based southern rock elements as well as influences from 70s heavy rock and dark psychedelia, Black Cobra's Invernal has been injected with a considerable dose of aggression, as Black cobra combine the crushingly heavy sound of sludge metal, attributed to downtuned and heavily distorted bass and guitars, with the tempos of thrash metal, and even some of the brutal riffing of early and primitive death metal. And this combination works quite well. The sludgy sound and uptempo aggressive beats and riffage amount to a very intense and chaotic sound which suits the tunes on the album extremely well. There are, of course, the obligatory heavy passages every now and then, but this album is by far dominated by brutal aggression. If you like both sludge metal and thrash metal, you should love this release, which, dirty, aggressive and sludgy as it is, should also appeal to fans of the likes of Down, Superjoint Ritual, Dead in the Dirt, and Elitist.