Black One is the fifth album by Sunn O))). As the title implies, the album is very black metal-influenced; utilizing many guest musicians of the genre including Malefic and Wrest from Xasthur and Leviathan respectively. Allegedly Malefic, a sufferer of claustrophobia, was locked in a casket during his recorded performance to the vocals on the track "Báthory Erzsébet". 2,000 copies included a bonus disc titled Solstitium Fulminate, containing a mix of live performances recorded at Roskilde Festival in 2005 and the immediately preceding European tour.