Mastodon is an American heavy metal band from Atlanta, Georgia, formed in 2000. The group is composed of bassist Troy Sanders, guitarists Brent Hinds and Bill Kelliher, and drummer Brann Dailor, all of whom perform vocals in studio (with the exception of Bill Kelliher). They all perform vocals at live shows. Their musical style features progressive concepts and unique instrumentation.

The band's second full-length album, Leviathan, was released in 2004. It is a concept album loosely based on Herman Melville's novel Moby-Dick. The band received critical acclaim for Leviathan and the record was named album of the year by Kerrang! and Terrorizer. "Blood and Thunder" which featured Clutch vocalist Neil Fallon was chosen as one of the most important recordings of the decade by National Public Radio in November 2009, and that the entire album epitomizes " a phenomenal decade for metal". Leviathan also ranked second in a list by Metal Hammer of the best albums of 2004.  The band went on tour in support of the album, playing throughout North America and Europe in The Unholy Alliance tour along with Slayer and Lamb of God and later on with Slipknot.  "Iron Tusk", the fifth track on the album, can be found on the soundtrack of the skateboarding video game Tony Hawk's American Wasteland and in 2K Sports video game NHL 2K9. "Blood and Thunder" is featured in the video games Need for Speed: Most Wanted, Project Gotham Racing 3, and Saints Row. "Blood and Thunder" was added as a playable track on all instruments in Guitar Hero: Metallica and was featured in Japanese music games Drummania V2 and Guitarfreaks V2. It has also been released as downloadable content for Rock Band 3, with Pro Guitar support also available at extra cost.  Leviathan was followed by the 2006 release of Call of the Mastodon, a remastered collection of the band's first nine songs, and a DVD of interviews and concert footage called The Workhorse Chronicles that includes material from the band's early days as a five-piece. The band has stated that "Call of the Mastodon" is their third studio album even though the album is a compilation album. These two releases were the band's last for Relapse Records, as they would later go on to sign with Warner Bros. Mastodon also recorded a cover version of Metallica's "Orion" for a 2006 Kerrang! tribute album marking the twentieth anniversary of the release of Master of Puppets.Answer this question using a quote from the following article:

How many albums did they sell.