Schatz der Kobolde (2010)

From the back of the box:

Once every hundred years rare lucky crystals grow overnight in the valley of the goblins! However, only Wutzel, Wanda, Wimmel and Wommel know the way to the crystal treasure. But the little goblins are invisible. You can see them with the help of the big magic crystal! However, they will only show the way to the lucky crystals to those who call them by their proper names.

Goblins Treasure - the goblins memory game with the unique magic crystal.

Players discover a rare crystal treasure in the valley of the goblins. Sixteen valuable lucky crystals are hidden all over the board and guarded by invisible goblins. A big magic crystal with a magnetic pendulum inside helps players identify the hidden goblins. Only correctly identified goblins will guide a player towards the hidden lucky crystals.