Cat Quest III

The Golden Tower dungeon is located at the north end of Purvanna. Upon entering you'll get a key for the first floor, but won't be able to access any others. You aren't given much info on how to obtain the keys to the other floors, but you can simply follow the video below to get them. Each one requires finding a specific gold coin on the map that will run away from you, and upon following it to the end of its pre-set path, a chest will spawn with the key inside. Collect all the keys, go back to the tower, and kill all the enemies inside to open each of the chests to complete the quest and unlock this achievement.