From 2002’s “The Best Ever Death Metal Band in Denton” to the lauded novel Wolf in White Van, underdog artisans have been John Darnielle’s favorite alter egos. His new Mountain Goats set draws its characters from the world of small-time wrestling. Expecting jokes? Think again. A battered dude poignantly remembers golden years (“The Ballad of Bull Ramos”); another prepares to finally reveal his true self (“Unmasked!”). The music is fantastically rangy, with discordant strings and jazz piano nuzzling punk-busker guitar. That WWF road-trip playlist you made with Springsteen’s “The Wrestler” just got way more interesting.