Mastodon has taken hold of the leadership of the New Wave of Progressive Heavy Metal. The band's 2006 major-label debut Blood Mountain spun off a Grammy nomination and earned Top 5 Best Album Of The Year nods from Kerrang!, Revolver and Metal Hammer, and a Top 10 Rolling Stone. Now Crack The Skye, its fourth original studio album, mines subject matter from czarist Russia and astral travel to out-of-body experiences and Stephen Hawking's theories on wormholes for an unrepentantly heavy aural assault that will shake the heavens.