Good solid idea, I put stuff like this in the ideas section, but that is just me. A basic 3.0 for being old and usable.
As others have said - a good, simple, and useful idea. Could be useful in a "find the dingus" adventure, where the players must track down the tuner stone so they can find the marker stone, which has been buried near the dingus.
Plots (Discovery) (Mini-Campaign)
Perhaps the sword inspires heroic acts, and after comming into contact with the magic, and evil of Vrin, was corrupted.
Slowly the sword is enhancing the combat ability of the farmer, but at the same time taking his mind and making him increasingly paranoid.
In the end he suspects all of attempting to revive Vrin, and will begin to try and use his newfound power to "prevent" this from happening. Go to Comment