Mastodon's punishing second album doubles as a concept album inspired by Herman Melville's allegorical novel Moby-Dick. As it turns out, Ahab's single-minded fixation with killing the white whale is perfect fodder for the band's relentless sonic barrage. Guttural vocal growls and shape-shifting drums provide the backbone for slabs of grinding fret calisthenics ("Blood and Thunder"), sludgy metal ("Iron Tusk") and lilting prog ("Seabeast"). Only the closing instrumental "Joseph Merrick"—a chilly acoustic meditation with grimy organ echoes—offers a tranquil respite from the storm.