Black metal has assimilated into the alternative American mainstream. Bands have borrowed from its bleak palate and turbulent speeds, and in return, black metal bands have evolved to include lush, ambient drones and orchestral arrangements — a far cry (or howl) from the sharp and impenetrably cold albums of the genre's designers some 30 years ago. In the U.S., the genre's most fertile landscape for reaping a new generation of sonic, doom-ridden chaos is on the West Coast, where bands like Washington's Wolves in the Throne Room have earned critical acclaim for meditative (and, of course, brutal) compositions, and California's Ash Borer, which preludes its skin-crawling assault with patient, precise riffs and enough atmosphere to create its own planet. The band's Bloodlands (Profound Lore) is technically an EP (just two songs), but at nearly 40 minutes, it's a hypnotizing, spell-binding reflection exercise and a white-knuckle, cloak-wearing thriller. Another West Coast metal outfit, Hell, performs with Ash Borer at a showcase of the West's indomitable darkness. The Coltranes and Christworm open. Admission $8.