Bob Jack is a man connected to the Magic Stone spell.
He was a poor bumpkin that came into possession of a Magic Stone of teleportation. He used the stone to teleport to try to get wine, women and gold. It worked good the first few times he used it. But then it put him into increasingly more dangerous positions. It took him before a hungry lion, then he was in a Mage's chamber, and then he was left in a river. He tried rub it a few more times until one of the times he teleported to his death.