The mutants and villains are lining up.As Matthew Vaughn prepares to shoot origins pic “X-Men: First Class” for 20th Century Fox, the studio has closed a deal for Kevin Bacon to star as a lead villain. Fox and Vaughn also have cast Jennifer Lawrence — currently in theaters in Roadside Attractions’ “Winter’s Bone” — as Mystique, the blue mutant shapeshifter who grows up to be a villain. (Rebecca Romijn played Mystique in the first three “X-Men” pics.) Studio is remaining tight-lipped about Bacon’s role, though some fanboy websites have suggested he might play Mister Sinister. “First Class” toplines James McAvoy and Michael Fassbender as the young Charles Xavier and Erik Lensherr (Magneto), respectively. The origins story, conceived by Bryan Singer and penned by Jane Goldsman, follows McAvoy and Fassbender as young men discovering their powers. Singer, Lauren Shuler Donner and Simon Kinberg are producing. Also starring are Alice Eve, Caleb Landry Jones and Nicholas Hoult. Bacon is repped by WME; Lawrence, CAA.