The 1980’s birthed the evil twins of Metal – Black and Death. The latter has less controversy around it, yet its chroniclers are also often guilty of misplacing the original artists for either the more popular 2nd wave (think your Cannibals and Deicides), or center their attention on just the more popular of the 1st wave (Possessed, Death, Morbid Angel). It again took a global effort and many forms of evil thought to form a genre. 1985 to 1987 is a good period to start with.