The knight drinks from well 6 before meeting up with the dragon, thinking the dragon will give him water from well 7. The night bring sea/lake water for the dragon to drink, thinking the dragon will drink water from a well to cure himself. (I also found several flaws in this. What if the dragon gave the knight water from well 6? Or if the dragon gave the knight sea/lake water?)
If the first player puts a quarter exactly in the center of the table, then the person just needs to match where ever the devil plays on the oposite side of the board. This means the player will fill the very last open space and the devil will lose.