Last night, just a stone’s throw from Foxfire Elementary School, Yonkers’s Alder Mansion was getting dirty — in a 2007 Posh-’n’-Becks W magazine cover kind of way. The party was held in honor of the photographer Steven Klein, who is releasing a new makeup collaboration with NARS in October. Everything about the space evoked his aesthetic: Rooms throughout the house were dimly lit and filled with Klein “vignettes.” In one area, a squad of shirtless male models sat in fishnets, holding toy guns. In another, a model toyed with a G-string behind cloudy plexiglass (and eventually took the g-string off). Partygoers were so enthralled that I heard one woman say to another, as we left: “That was the sickest party of the year, in a good way.” Click through the slideshow to see François Nars, Steven Klein, Alexander Wang, Stephanie Seymour, Amanda Lepore, and more.