Blackened death metal (also called black death metal) is a style of death metal utilizing black metal elements. Many blackened death metal bands start out as full on black metal outfits and end up adopting death metal influences and fusing the two together, or becoming modern death metal artists.
In the 1980's, bands like Hellhammer and Celtic Frost straddled the often still-vague genres of thrash metal, death metal and black metal and it wasn't until albums such as Necrophobic's The Nocturnal Silence and Behemoth's Satanica that the current form of blackened death metal truly took form. Some melodic black metal bands have a style similar to blackened death metal, because it owes much to death metal (more precisely Scandinavian death metal and melodic death metal.)
Often cited musical characteristics of blackened death metal are relatively high pitched, raspy death grunts in a more black metal style, cyclical technical death metal riffs or simplistic black metal riffs, and extremely fast and often repetitive drum work with a more groovy approach than in black metal, which is a death metal influence.
Blackened death metal bands often have influences outside black / death metal. For example, Akercocke has also displayed avant-garde and progressive elements in their albums and Vesania are well known to feature orchestral arrangements mixed up with black / death metal. The lyrical content in particular draws more from the black metal discourse, with less emphasis on themes of gore and dismemberment popular in death metal. Like with traditional black metal, some critics have noted that particular bands seemingly real devotion to ideologies of a "blackened" nature makes them unintentionally comical. Despite this, the genre has a loyal following within the metal underground, although it is highly doubtful that many of the genre's consumers take the music/ideology hybrid as seriously as its practitioners. .