The Medici Tablet is the tablet on which the Fulfillment Spell is engraved.
The exact origin of the Medici Tablet is unknown though by the end of the 15th century it did belong to the famous Medici family, which dominated Florence, Italy during the Renaissance. 
Demona sought out the Medici Tablet and eventually located it in 1495. It was being kept hidden in a secret compartment in a building in Florence. She stole it and kept it in her possession for five hundred years and later used the Tablet as a key component for "Operation Clean Slate". After her plan was foiled by the Manhattan Clan, she abandoned the Tablet, which eventually wound up in the hands of the authorities. ("Hunter's Moon Part Two" and "Hunter's Moon Part Three") 
Behind the Scenes
In the early stages of writing the "Hunter's Moon" three-parter, Greg originally referred to the Medici Tablet as the 'Borgias Tablet,' in which he planned for Demona to steal the tablet from the Borgia family before being pursued by the Hunter Stuart Canmore.