A natural stone with a hole in the center and gift from the earth to the lucky finder.
A totally throw away .. cannon fodder ..shove it in the mouth of the monster and run for it type of character. Useful though for ‘taken with a pound of salt’ information and running small unsavory errands.
The idea of using tattoos to contain magic powers is not a new one. The Ink gauntlet follows the basic premise of using rare and precious inks to inscribe spells into the skin of a mage or would be spell-imbued person. Some of these inked spells might be permanent, while others might fade after being used once, or a preset number of times.