Jewels

Each of the twelve puzzles in The Secret incorporate a different jewel, which is featured in each of the paintings. These correspond to twelve actual jewels, which were purchased by Byron Preiss to serve as rewards for successful treasure hunters. According to the rules of the treasure hunt, the finder of a casque can remove the key sequestered within, and redeem it for the corresponding jewel.

The (fictional) provenance of each gem is given in the Litany of the Jewels.