Hellhammer was a Swiss metal band from Nürensdorf, active from 1982 to 1984. Although the band's sound and style were heavily criticized and poorly reviewed during their active years, they have been widely praised in retrospect and are often regarded as a key influence on black metal. In June 1984, Hellhammer disbanded but two of its members soon formed the influential extreme metal band Celtic Frost.

Source: Wikipedia (https://en.wikipedia.org/wiki/Hellhammer)