I don't see how the dragon could die, or the knight.
There is no SPOILER tag. Blah.
Let's see.
DRAGON :
Before the duel, the dragon drinks from well 5. After the duel, he drinks from well 6.
The knight can give :
Water from well 1-5
Plain water
If the knight gives water from well 1-5, this will have not effect on the dragon : he is still poisoned by well 5. He then drinks from well 6 and is cured.
If the knight gives plain water, the dragon is still poisoned by well 5. He then drinks from well 6 and is cured.
The dragon always lives.
KNIGHT :
Before the duel, the knight drinks from well 1. After the duel, he drinks from well 1, then from well 5.
The dragon can give :
Water from well 1
Water from well 2-6
Plain water.
If the dragon gives water from well 1, this will have no effect on the knight. He is still poisoned. He then drinks from well 1 (still poisoned by 1) and then from well 5 : he is cured.
If the dragon gives water from well 2-6, this will cure the knight from well 1. He is cured. He poisons himself with well 1, but cures himself with well 5. He is cured.
If the dragon gives plain water, the knight is poisoned by well 1. He then drinks from well 1 and is still poisoned by 1. Then, he drinks from well 5 : he is cured.
No matter what, both the dragon and the knight live. They then decide that this duel was stupid, and live happily together. When the knight finally dies of old age, the dragon decides to suicide to follow his friend to the realm of the dead. He drinks from the well 6, and dies.
THE END.
i believe this is the answer unless only the dragon or the knight can drink out of the well once but both of them can only one...
i believe this is the answer unless only the dragon or the knight can drink out of the well once but both of them can only one...
If the man is smart, he will break the well 5.
But, they don't need to duel. The dragon can just fly away or carry the men to another island.