There's a reason why he was the most famous wizard in history. Merlin was also a student at Hogwarts, and he left his legacy (never better said) around the grounds of Hogwarts Vale in the form of simple puzzles in which we have to destroy objects, carry fireflies to marked rocks or throw huge boulders and dunk them into stone holes. Whatever it is, the prize is worth the effort. Spaces for equipment inventory, which are very important because they are really limited, and because it also represents the biggest source of income in the game.