Dragon Fantasy: Volumes of Westeria

Story-related and cannot be missed.

This is received in Jerald's chapter. The bandit cave is west of Sandheim. The first floor consists of some decent shops, an expensive inn, and an outhouse you can save your game at. The cave entrance is south of the outhouse.

In the cave, if you are at a low level, you can ignore all the treasure chests as most of them are Bitey Boxes and will hit you hard for not a lot of reward. Also, there are no random encounters, so you can explore to your heart's content

On the second floor, make your way to the south east corner of the map and go down, then on the third floor, go north all the way, then west. Essentially, where you see two ladders separated by a space you can't cross, go up to the second floor and down the other ladder. You'll have to do this at two other places.

After the second time, follow the path and you'll see a ladder which leads down to a room filled with treasure boxes (filled with junk). The trophy will unlock here.

Note: If you are going for Grind it Out, do not open the chest directly north of the ladder in this room. Honestly, you don't really need to open any of the chests. All of the 'treasures' found sell for 10 G except for a Gold Sword.