In Sorte Diaboli (Latin for "On Behalf of the Devil") is the seventh album by the Norwegian black metal band Dimmu Borgir. The album was released in 2007 via Nuclear Blast. In Sorte Diaboli is the band's first concept album. The story is set in medieval Europe. The protagonist is a priest's assistant who first doubts his faith and then turns to the dark side, becoming the Antichrist. The story is told in the form of a diary. This led to the idea of beginning each song title with the article "The." Guitarist Silenoz first gathered ideas for the concept album during the 2004 Ozzfest tour. The album was recorded between October and December 2006 at Studio Fredman. In Sorte Diaboli was produced by Frederik Nordström, Patrik J. Sten, and the band themselves.