Chains of Destiny
The coin of the dead, made from the dead, their plasm pressed into molds and hammered into shape by the smiths of the Hierarchy. It is said that the wraiths these coins are made from may still be conscious or aware on some level, a thought that is too horrid for words. Most wraiths avoid thinking about this as much as possible.
Oboli are sometimes carried by Bo, like any other Wraith worth his plasm.