I pieced together the Bricklink Mountain Fortress from our parts collection. It has some substitutions, especially arches and snow pieces. It took me about 3 months to build- first digging through our parts drawers, tracking the pieces we don’t have, and a bunch of visits to Bricks and Minifigs to dig through their selection of pieces, then building for an hour at a time after work and putting kids to bed. My preschooler repeatedly broke off parts - so there are missing internal details...