Around 30 seconds into "Bladecatcher," track six of Mastodon's new album, things go so far into left field that it might be necessary to stop the CD and back up to follow what just happened. That moment—a gnarled, hyperspeed squeal where the band's vocals (if that's what they are) congeal into an alien-tongued mass—is one of Blood Mountain's several utterly disorienting highlights. It's also proof that Mastodon didn't soften when it left its longtime indie-label home, Relapse Records, for Reprise's fatter coffers. If anything, the jump to the majors has provided the art-metal quintet with the Hieronymous Bosch-scale canvas on which it can finally unload the full terror of its vision.

Granted, some moments on Blood Mountain are friendlier than any previous Mastodon work: the melodious, stoned-out grooves of "Colony Of Birchmen" (featuring Queens Of The Stone Age's Josh Homme), for instance, or the Iron-Maiden-on-steroids feel of "The Wolf Is Loose." And it's actually good to hear gravel-throated vocalist-bassist Troy Sanders singing for a change, as he does throughout much of the album. But for every such endearing moment, there's the lysergic-nightmare metal of "Circle Of Cysquatch," the shearing waves of guitar on "Capillarian Crest," the slithering, serpentine "Siberian Divide" (featuring The Mars Volta's Cedric Bixler-Zavala), or the waves of rhythm on "Hand Of Stone," which find drummer Brann Dailor seemingly conjuring up falling buildings. Blood Mountain is terrifying in scope as well as execution, with the monsters that haunt Sanders' lyrics only growing stronger and more vivid off the inhuman performances that support them.