This stretch of MCU caches are hidden along the publicly-accessible snowmobile trails maintained by the Perkins Ridge Sno-Travelers. These trails are open to hiking, snowmobiling, snowshoeing, skiing, horseback riding, and dog sledding. No knowledge of the MCU is required for these caches; they are along the lines of the Alien Invasion caches.
In the comics, Zebediah Killgrave is the Purple Man - a villain with purple skin who can make others do as he says, even against their own will. A modified version of the character calling himself Kilgrave appears in Jessica Jones, portrayed by David Tennant.