Permanent Magic Items

One of the settings I intend to convert to the Renaissance system requires permanent

magic items and the player characters' ability to design and create such items, and I

am currrently looking for a way to make this possible with the right "feel" for the game

system.

At the moment I think I will introduce an "advanced" kind of Philosopher's Stone, more

difficult to create than a normal one, but able to draw "magickal energy" from the en-

vironment and use it to power a magic item. In theory this kind of Philosopher's Stone

could function indefinitely, but since it is impossible to create a perfect stone each of

the stones has a "burn out probability", which is determined during the creation of the

stone and rolled for each time the item powered by the stone is used. Once the item's

stone has burned out, it has to be replaced with another advanced stone of the same

power to make the item function again. Each advanced stone is made for one specific

item, it cannot be used to power any other item.

I think that this concept would fit into the "feel" of Renaissance's system of Alchemy,

but I am not yet sure - comments would therefore be most welcome.