In early May 2017, I walked out of the small airport in Ljubljana, Slovenia, carrying two giant duffels and a ski bag. An orange Land Rover pulled up to the curb. Out climbed Davorin “Davo”  Karničar, the only man to ski Mount Everest from top to bottom. We’d never met, but Karničar shook my hand and smiled like we were old friends. His biceps and chest bulged out of his T-shirt.  A few minutes later, we began the short drive to Jezersko, the 600-person farming village where Karničar had lived all his life—and where he died Monday, September 16, in a tree-felling accident at age 56. (Jeff Mechura, president of Elan USA, Karničar’s longtime ski sponsor, confirmed his cause of death on Tuesday.) We snaked along the Kokra River, clear and pure, talking as we went. His English wasn’t great—“expedition English,” he called it—but his cheerful spirit made up for it.  An unlikely turn of events had brought us together: one month earlier, having heard Karničar was preparing to attempt the first full ski descent of 28,251-foot K2, I emailed him requesting an interview. He wrote back a few hours later with what he called “a proposition.” Instead of doing the interview by phone, he could fl...