[HEAVY METAL] Witch Mountain's past two albums have traced a stylistic devolution—not a regrettable situation, seeing as the Portland-based sludge-metal quartet (which features WW contributor Nathan Carson on drums) has defined its 15-year career by teaching new tricks to the old dogs of metal's thunderous roots.

Following close on the heels of 2011 comeback album South of Salem, Cauldron of the Wild continues Witch Mountain's process of reverse aging. Behind the story-song mythos of "Lanky Rae" and the foot-dragging fuzz of "Shelter" hides a devotion to the Precambrian forms of metal that still made an open secret of their debts to blues and psychedelic rock. 

Cauldron of the Wild takes Black Sabbath's down-tempo grind and follows the style to its logical endgame. The shortest of the LP's six tracks clocks in at 5½ minutes, a natural consequence of composing your songs exclusively from breakdowns. Whereas on previous releases, Witch Mountain made room for occasional interludes of technical thrashing, Cauldron of the Wild relegates its sonic interest solely to the dirge.

As on South of Salem, Ula Plotkin's vocals steal the show. Able to produce back-to-back Platonic examples of a crystalline, Valkyrie's alto as well as a subdemonic growl, Plotkin serves as the deciding factor in pushing Witch Mountain a head above its doom-metal compatriots.

Cauldron of the Wild closes out with "Never Now"—a nine-minute slow-burner that cuts Plotkin loose near the five-minute mark and lets her tear her way through the track's remainder like a gale-force wind. On an album predisposed to overdosing on its colossal scale, it's impressive that its best moments can still stand out as legitimately epic.

SEE IT: Witch Mountain plays Backspace on Saturday, June 23, with Lord Dying and Spellcaster. 9 pm. $10. All ages.