Reward: Tear of Avo.
You will encounter this quest only if you destroyed the Sword of Aeons after fighting Jack of Blades. The sword you find is thought to be it's "good" equivalent, as its stats are exactly the same. Go to the Guild.
Guild Master will tell you to go to Maze's room. Search through the bookshelves and then head to the middle of the area, where the four graves are. Examine the eastern grave and the sword will be yours. Doh, that was complicated.