Monotheist is the fifth and final studio album by the Swiss extreme metal band Celtic Frost. The album was released in May 2006 and was the first new recording released by the band in 16 years. Upon its release, the album was met with critical acclaim. Development Preparation and development work for the project had been ongoing since 2000. The first recording sessions for the album started in late October 2002. The band consisted of founding members Martin Eric Ain (bass/vocals) and Tom Gabriel Fischer (voice/guitars/keyboards), along with guitarist/producer Erol Unala, Fischer's long-time songwriting partner. Unala became an increasingly significant part of Celtic Frost during the songwriting. Working titles for the album included Probe and Dark Matter Manifest. "Obscured" comes from the demo track "November" from the 2002 demo album "Prototype". "Drown in Ashes" uses lyrics from the demo track "The Dying I". Music Celtic Frost's earlier work melded elements of thrash metal and black metal. The sound of Monotheist has been described as difficult to reduce to specifics, as the songs vary from doom metal to "blackened thrash" to gothic metal to symphonic metal. The result is a wide-ranging but very dark heavy metal experience. Don Kaye of Blabbermouth called it "a monstrously heavy and oppressive slab of metal" which goes "into even heavier, blacker territory" than previous albums. Adrien Begrand of PopMatters said that the album was nearly a masterpiece of "brutally heavy" metal, "completely devoid of light". Eduardo Rivadavia of AllMusic noted more subtle touches such as the "instantaneously infectious melody" of "A Dying God Coming into Human Flesh", and the "haunting female voices" heard in duet with bandleader Tom Warrior on "Drown in Ashes". According to Fischer, some of the lyrics were influenced by the writings of the English occultist Aleister Crowley. This influence manifests itself in tracks such as "Os Abysmi Vel Daath", which is the partial name of one of Crowley's books. Release Monotheist was released on CD and LP. A limited edition digipak featured the bonus track "Temple of Depression". Both the vinyl LP version and the Japanese CD release of Monotheist feature the bonus track "Incantation Against You". A video was made for the song "A Dying God Coming into Human Flesh". The album was ranked number 2 on Terrorizers list of the best albums of the decade. Track listing Credits Thomas Gabriel Fischer – vocals, guitars, arrangements, programming Martin Eric Ain