Birthright!
Reading this thread reminded me of an awesome Birthright adventure from Dungeon magazine issue #59 by Chris Perkins, "Seeking Bloodsilver". It was a great adventure that I ran even though I didn't have any of the campaign setting books.
I searched and found a cool web site devoted to it:
http://www.bloodsilver.com/
Here is some information that I lifted from it:
Bloodsilver: Also known as tighmaevril ( tie-MEE-vril ). A secret blending of metals and other qualities which the ancient elven smith Ghoigwnnwd, alone in the world, was able to manufacture. The alloy is notorious amongst the scions of Aebrynis, for with it, a man can sever the very bond between regent and domain, casting the land into chaos and despair all around him, and stealing for himself, like a leech to a wound, the very essence of divinity which has been passed between king and heir since the fall of the Old Gods at Deismaar.
Anyway, there's an option for your mysterious weapons. If I were in your DM shoes, I would make them all masterwork (possibly mithril) and give xp value equal to their GP value to the PCs for destroying them as they bear those evil markings--especially that paladin, he kicks @$$! If they sell them off, they should suffer all manner of direct & indirect consequences: from xp penalties to having to fight evil-doers bearing those weapons forever (BBEGs or very powerful servants of them--they may even take these pristine implements and enchant them for dark powers and purposes).