It’s pointless to quibble over authenticity when you’re talking about a band that’s been through 18 members and includes only one founder. But when it comes to old-school death-metal, the only things that really count are chops and execution. Vader are still slinging in the trenches on Necropolis, which proves that after eight solid albums, they’re at the top of their game. Everything about Necropolis is old-school, from the groove-oriented riffs and pummeling drums to the mean, gritty guitar tones. And unlike most contemporary deathcore groups, Vader, who hail from Poland, don’t bother with breakdowns or songs that run more than four-and-a-half minutes (most clock in around two or three). The album comes in, destroys and leaves in about 30 minutes — just like a good death-metal album should. Vader are part of Decibel magazine’s Nuclear Blast Winter 2009, which also features Warbringer, the Amentia and others. The band comes to Peabody’s (2045 E. 21st St., 216.776.9999) at 7 p.m. Tickets: $14 advance, $17 day of show. — Nick DeMarino