With its dystopian hook and 10-ton impact, “Insane” is the perfect gateway to this recharged offering from nu-metal’s most influential band. Anyone who thinks fame and fortune have mollified Korn needs to hear “Rotting In Vain,” a raging release of Jonathan Davis’ innermost animosities. Slipknot’s Corey Taylor shows up for the outstanding “A Different World,” but the band saves “Please Come For Me”—its fiercest, most economical attack—for last.