With a sound that can only be described as the sonic equivalent of armageddon, here comes England's Anaal Nathrakh. They burst onto the scene with two demos in 1999: their self-titled one in March of 1999 and Total Fucking Necro in September of the same year. Gorgoroth's Destroyer meets Marduk's Panzer Division Marduk is about the closest black metal sound I can think of for people who want to know what they sound like. And on this demo, AN absolute destroy everything in their path! The sound quality is damn good (especially bearing in mind that it is a DEMO), and there is a Mayhem cover ("Carnage") on it, but other than the two references above (Marduk and Gorgoroth) there really is no band that sounds like Anaal Nathrakh.
Continuing the evil that they began with their self-titled demo, Anaal Nathrakh not only perform their blackened chaos metal but they do a very faithful cover of Mayhem's "De Mysteriis Dom Sathanas." I am absolutely blown away by everything these Brits do. A guitar sound that is reminiscent of Gorgoroth, Obtained Enslavement, and even the godfathers themselves, Mayhem, AN are truly, IMHO, black metal for the new millenium. I heartily recommend that you get these two demos! They were re-released in 2002 on one disc on Rage of Achilles records.