Raven Stones
Raven stones are in German folklore, magical lights made from the undigested eyes of executed criminals. Raven stones are so named because they are obtained from ravens that picked out the eyes of corpses hanging on gallows.
According to lore, raven stones emit a light visible only to their owners and are used by thieves.
From :The Encyclopedia of Magic and Alchemy Written by Rosemary Ellen Guiley Copyright © 2006 by Visionary Living, Inc.