Nocturnus was formed in Tampa, Florida in 1987 by drummer and vocalist Mike Browning, a former member of Morbid Angel, and built a sound around science fiction themes and prominent keyboard use at a time when such elements were virtually absent from extreme metal. Their 1990 debut The Key, recorded at Morrisound and released on Earache, is widely credited as one of the first progressive death metal albums and remains a landmark in the genre's development. The band dissolved after internal conflicts and Browning later revived the project as Nocturnus AD, releasing a long-awaited sequel to The Key's narrative in 2019.