There are two bands under this name (not to be confused with the German Nagelfar):
1) Naglfar is a Melodic Black Metal/Blackened Death Metal band from Umeå, Sweden. The group was formed by Jens Rydén and Kristoffer Olivius, originally under the name "Uninterred". The group's style combines traditional Black Metal with certain Melodic Death Metal elements.
Naglfar formed in 1992. The band was originally called "Uninterred", and was founded by Jens Rydén on vocals and guitar, and Kristoffer Olivius on bass. The band had its first full line-up when Ulf Andersson from Nocturnal Rites joined the band to play drums, and Morgan Hansson and Fredrik Degerström joined on guitar. With this new line-up Jens could concentrate on vocals. In March of 1994, Fredrik left Naglfar due to personal issues with the band as well as musical differences. Soon afterward Ulf left the band as well so that he could concentrate on Nocturnal Rites. It was during this tumultuous period which the band was writing and recording their first demo in Garageland Studio, titled Stellae Trajectio. The demo was released in November of 1994. Before it was publicly released, however, the band officially changed their name to Naglfar.
In early 1995, the band was signed by Wrong Again Records, and that summer they released their debut full-length album, Vittra. After the recording was over, Mattias Holmgren left the band. Other than appearing on an Iron Maiden tribute CD (they performed the song "The Evil That Men Do"), the band was relatively inactive for the next few years. Their sophomore album, which received strong reviews, was titled Diabolical and released in 1998. After more line-up changes, Naglfar recorded an EP called Ex Inferis, and a full-length called Sheol.
In 2005 vocalist Jens Rydén left the band for educational reasons. Bass player Kristoffer W. Olivius takes over the microphone, also known from the swedish black metal extremists Setherial.
In 2005, their fourth full-length album Pariah was released with such black metal masterpieces as "Spoken Words of Venom" and "Revelations Carved In Flesh". They also did a video for the track "The Perpetual Horrors".
Morgan Lie joined the band as bass player in late 2006.
Their fifth full-length album Harvest was released in spring 2007.
After Harvest was released and some gigs were thrown Naglfar took a break. No news have been heard from them in a long time. Their website went under reconstruction at some point, and has never since been opened again. Their current website has only a link to their myspace page. Rumours about them disbanding have been around since winter 2007.
2. Naglfar is a dark metal band from Norway. Their music has a slight black metal aesthetic, but the band vehemently denies any connection to that scene.