Key received. To install it, follow the yellow arrow.
By hitting the trigger next to ramp below the Shaman, a switch is thrown that allows you to go on a quest for a key when entering the ramp. The quest will be randomly selected and marked by a yellow arrow. You then have 2 minutes to install the key or it will be lost. If successfully installed, the key simply rotates the Labyrinth, similar to lighting up the targets that do the same, however keys always move the ball towards the opening in the next ring.