question: Which vocalist left the band whose fourth full-length album is Destroyer?
answer: Kristian Eivind Espedal
context: Title: Destroyer (Gorgoroth album)
  Passage: Destroyer – or About How to Philosophize with the Hammer is the fourth full-length album by Norwegian black metal band Gorgoroth.  It was their first release on Nuclear Blast.  It contained eight tracks performed by several different lineups, with band founder Infernus being the only member to be featured on all tracks.  Four different vocalists were featured on the album, including Infernus on two tracks, Pest on four tracks, and T-Reaper and new vocalist Gaahl each on one track.
  Title: The Fourth Legacy
  Passage: The Fourth Legacy is the fourth full-length album by power metal band Kamelot.  It was released in 1999 by Noise Records/Modern Music.  It was the first album to credit vocalist Roy Khan as a writer on all tracks, establishing him as the main songwriter of the band together with founder and guitarist Thomas Youngblood.
  Title: Oh, Sleeper
  Passage: Oh, Sleeper is an American Christian metalcore band from Fort Worth, Texas that forged themselves in 2006 with ex-members of Between The Buried and Me, As Cities Burn, and Terminal.  In over a decade's span, Oh, Sleeper released three full-length albums and two EPs through Solid State Records, and toured worldwide as an opening act.  After independently releasing "The Titan EP" and travelling in the full Van's Warped Tour 2013, the band went on hiatus to allow clean vocalist and lead guitarist Shane Blay to join former-As I Lay Dying members in starting California-based metal band Wovenwar.  The band plans to release their fourth full-length album release, "Bloodied//Unbowed" in 2017.
  Title: The Maine (band)
  Passage: The Maine is an American rock band from Tempe, Arizona, formed in 2007.  Their first release, the EP "Stay Up, Get Down" was released in late 2007, followed by a five-song EP titled "The Way We Talk" on December 11, 2007.  The band's first full-length album, "Can't Stop Won't Stop" was released July 8, 2008. " ...And a Happy New Year" was released in December 2008.  Their second full-length album, "Black & White", (July 13, 2010) sold 22,634 copies in its first week.  On December 6, 2011, the group's third album, "Pioneer", was released and it peaked at No. 90 on the Billboard 200.  Their fourth full-length record "Forever Halloween"(June 4, 2013) reached No. 39 on the Billboard 200 by selling over 10,000 copies in its first week and was followed by its deluxe edition on June 17, 2014.  Their fifth studio album, "American Candy", was released on March 31, 2015. " Lovely Little Lonely", their sixth full-length record, was released on April 7, 2017.
  Title: Gaahl
  Passage: Kristian Eivind Espedal (born 7 August 1975), better known by his stage name Gaahl, is a Norwegian vocalist and artist.  He is best known as the former frontman of Norwegian black metal band Gorgoroth.  He is also the founder and frontman of Trelldom and Gaahlskagg.  Since leaving Gorgoroth he has been involved with God Seed, Wardruna, and Gaahls Wyrd.  He was the focus of the documentary "True Norwegian Black Metal" and also appeared in the film "Flukt".
  Title: Fireflight
  Passage: Fireflight is an American Christian rock band formed in Eustis, Florida in 1999.  The band is signed by Flicker Records.  They have played in ShoutFest, Revelation Generation, and have been featured on The Scars Remain tour with Disciple, Family Force 5, and Decyfer Down.  While touring, they wrote their third album, "Unbreakable" (2008), and released their first single off the album, "Unbreakable".  They performed at Winter Jam 2010 and released their fourth full-length album "For Those Who Wait" in February.  On December 1, 2010, they were nominated for their first Grammy award.  In 2012 they came out with their fifth full-length album "Now".
  Title: In the Unlikely Event
  Passage: In the Unlikely Event is the fourth full-length album by American progressive rock band The Fall of Troy, that was released on October 6, 2009.  The album was recorded with producer Terry Date and is the only full-length album to feature bassist Frank Ene (first featured on "Phantom on the Horizon").  It was recorded at Studio Lithio.  The album featured a slightly less aggressive style compared to the band's earlier work, in turn facing mixed critical reception.
citations: Gaahl Destroyer (Gorgoroth album)