The band's name is derived from the German word Nacht meaning "night", and the made-up term mystium which resembles the Latin adjective mysticum. Judd and McCormick combined the words to create the band's name, which they state means "Encompassing Darkness".
Nachtmystium was originally founded by Blake Judd and Pat McCormick as a side project. The band was heavily influenced by second-wave black metal bands, such as Darkthrone and Burzum, evidenced in their low-fi first release Reign of the Malicious in 2002. The band’s next release, Demise (2004), was described by Judd as Nachtmystium's "last straight forward 'raw black metal' record." The band's following two releases, Eulogy IV (2004) and Instinct: Decay (2006), incorporated psychedelic and experimental musical elements that were pioneered by bands like Black Sabbath, The Doors and Pink Floyd. Instinct: Decay received general positive feedback from critics. DEAF SPARROW Zine, praised the album for its innovation, while Decibel Magazine went even further to name Instinct: Decay as the fourth best album of 2006. The band released Assassins: Black Meddle, Part 1 on June 10, 2008 in America. The album received a generally positive critical reception, especially from Pitchfork Media and MTV's Headbangers Ball, who both stated that it was one of the year's best releases. The band played their first Scandinavian show in Bergen, Norway at the 2008 Hole in the Sky Festival with At the Gates, Municipal Waste, and Meshuggah. Nachtmystium toured with Opeth, Baroness, and High on Fire for the first half of their American tour. In September 2008, the band confirmed plans to release a remastered version of Demise, with two extra tracks. Nachtmystium has also announced plans to release a new EP, entitled Doomsday Derelicts, early in 2009. The band experienced two major setbacks in February and March 2009. Nachtmystium was forced to withdraw from the Scion Rock Fest in Atlanta, Georgia due to alleged connections to National Socialist black metal (see Connection to NSBM section). Later that month, Judd injured his leg, forcing the band to cancel their tour with The Haunted.
In September 2009, Nachtmystium announced plans to release a follow up album to Assassins: Black Meddle Part 1 with an album titled Addicts: Black Meddle, Part II. Judd commented that the album would feature new material with "more of a rock and roll edge over all", and reflect the bands interest in post-rock and industrial music. The album debuted on June 8, 2010. The band played at the Inferno Festival in Oslo, Norway, on April 3, 2010, where they shared the stage with Mayhem, Finntroll, and Taake.
Nachtmystium began recording a new full-length album spring 2011. The new album will be the third installment in the Black Meddle series, and will feature a sound similar to Addicts: Black Meddle Part II. The band also released a live recording of their performance at Roadburn Festival. This was Nachtmystium's first full tour with live synths.