On Saturday, March 30th, three previous members of Dimmu Borgir — bassist / clean vocalist ICS Vortex (real name: Simen Hestnæs), keyboardist Mustis (real name: Øyvind Mustaparta) and drummer Tjodalv (real name: Ian Kenneth Åkesson) — rejoined the Norwegian symphonic black metal band during their headlining set at the Inferno Festival at the Rockefeller Music Hall in Oslo, Norway to perform the song "The Insight And The Catharsis", from their 1999 album Spiritual Black Dimensions. Fan-filmed video of this special event can be enjoyed below.

In 2009, ICS Vortex and Mustis independently announced their departure from Dimmu Borgir. Mustis released a statement claiming his disfavor with the band, stating that he was not properly credited for his writing contributions to the band's music, and mentioned the possibility of taking legal action.

Shortly thereafter, Dimmu Borgir confirmed the pair's dismissal from the band, releasing a statement explaining why the two were fired. Shagrath, Silenoz and Galder wrote: "Funny then, how the new album is half-way finished written already by the rest of us without any of these guys' input, still having all those elements we're known for."

Dimmu Borgir's current lineup is officially a trio comprised of vocalist Shagrath (real name: Stian Tomt Thoresen), rhythm guitarist Silenoz (real name: Sven Atle Kopperud), and lead guitarist Galder (real name: Tom Rune Anderson). They are joined by session musicians Dariusz "Daray" Brzozowski on drums, Geir "Gerlioz" Bratland on keyboards, and Victor Brandt on bass.