The small green cube that is similar to a credit card in the Lost Cities. Lusters are the elves' currency. One Luster is equivalent to about 1 million human dollars. At birth, every elf is given a treasury cube with a birth fund of 5 million luster. To pay lusters to another elf, one would swipe the treasury cube against a machine called a Deducter. To add money to the cube, an elf goes to the Treasury.