These items can be purchased from the Auction House. They drop from the following varieties of Quadav: Amber, Brass, Greater, Old, Onyx, and Veteran. Palborough Mines is a great place for farming due to the high density of Quadav; you need only ignore Amethyst, Copper, and Young Quadav.
The cutscene will differ notably depending on which Bastok Gate Guard you trade the items to. To view all of the cutscenes you will need four sets of items; however, as they are , you will need to farm each set one at a time.
Optional: Talk to Gumbah (J-7) in an upper-level house in Bastok Mines for an extra cutscene.
Hunt the Quadav in the Palborough Mines and collect the four parts of a Quadav fetich.
SPOILER WARNING: Click here for additional details about this story line.