"Push it push it push it!" Alexis Krauss shouts at the beginning of Reign of Terror, and that's exactly what she and Derek Miller do on their follow-up to Treats. Despite its in-the-red volume, Sleigh Bells' debut was a fragile, almost alchemical blend of wispy melodies and crushingly heavy beats and riffs. How could they top an album that was already turned up to 11? By turning things up to 12: on Reign of Terror, the duo brings the nods to metal that added a headbanging thrust to Treats and to center stage. From the album’s name down to song titles like “D.O.A.” and “Never Say Die,” Krauss and Miller allude to metal’s flirtations with death, which makes a strange kind of sense: Treats was a blend of sounds that shouldn’t have worked but did, and changing that formula is riskier still. Oddly, though, the duo sound more gimmicky with a narrower focus than they did when they were tossing drumline beats and P-Funk samples into the mix. With Miller playing a shred and squeal-friendly Jackson USA Soloist and a slicker production, Reign of Terror has a chilly, harsh edge that makes Sleigh Bells’ debut sound downright quaint by comparison.