Given the question: Found the following article online, use it to answer the question: What four bands went on a worldwide tour together?  Opeth entered Fascination Street Studios in November 2007 to record their ninth studio album, with Åkerfeldt producing. By January 2008, Opeth had recorded 13 songs, including three cover songs. The finished album, Watershed, features seven tracks, with cover songs used as bonus tracks on different versions of the album. Watershed was released on June 3, 2008. Åkerfeldt described the songs on the album as "a bit more energetic". Opeth toured in support of Watershed, including headlining the UK Defenders of the Faith tour with Arch Enemy, an appearance at Wacken Open Air, and the Progressive Nation tour with headliner Dream Theater. Watershed was Opeth's highest-charting album to date, debuting at number 23 on the US Billboard 200, on the Australian ARIA album charts at number seven and at number one on Finland's official album chart. Opeth went on a worldwide tour in support of Watershed. From September to October, the band toured North America backed by High on Fire, Baroness, and Nachtmystium. They returned to tour Europe for the rest of the year with Cynic and The Ocean.In 2010, Opeth wrote and recorded the new track, "The Throat of Winter", which appeared on the digital EP soundtrack of the video game, God of War III. Åkerfeldt described the song as "odd" and "not very metal." To celebrate their 20th anniversary, Opeth performed a six-show, worldwide tour called Evolution XX: An Opeth Anthology, from March 30 through April 9, 2010. Blackwater Park was performed in its entirety, along with several songs never before performed. The concert of April 5, 2010, at the Royal Albert Hall in London, England was filmed for a DVD and live album package titled In Live Concert at the Royal Albert Hall. The set was released on September 21, 2010, in 2-DVD and 2-DVD/3-CD configurations. For the DVD the concert was split into two sets. The first set consists of the entire Blackwater Park album, while the second set contains one song from every album excluding Blackwater Park, in chronological order representing the...
The answer is:
Nachtmystium