There are several forms of death metal out there. There is the obvious gore-obsessed death metal from acts like Cannibal Corpse. There is highly technical and brutal death metal from bands like Suffocation. Then there are the overtly evil bands. Let's look at three of the leaders from the occult death metal movement.
Morbid Angel is the originator and most well-known of the sub-genre. Morbid Angel is also one of the first death metal bands ever. They arose out of the mid to late 1980's playing a heavier, more complex, and evil sounding style of thrash metal that then came to be known as death metal. Their lyrics were focused on Satanism and other occult themes. The vocals were extreme, much huskier than thrash metal shrieks, but death metal had not gotten to the guttural vocal style now familiar. Morbid Angel actually proved fairly popular in the early 1990's when thrash, and metal in general, was struggling.
Incantation took the Morbid Angel formula, added some doom elements and ran with it, to become perhaps the most evil-sounding band to date. Incantation's music is frightening. Slow, with jagged riffs, guttural vocals, heavy bass sound, murky production, and pounding drums. Incantation's leader John McEntee also owns and operates Ibex Moon Records, a label devoted to putting out releases from powerful death metal, acts like Dreaming Dead, Dawn of Azazel, Thornafire, and Estuary.
Immolation is only slightly less frightening than Incantation. They don't have the doom metal elements that make Incantation stand out, instead choosing a more straightforward death metal approach forged by Morbid Angel. Immolation has a knack for infectious, yet extremely evil lyrics and songs.
Others playing this style: Blaspherian, Drawn and Quartered, Nox, Angelcorpse, Thornafire.