The point of the game is to fulfil the prophecy from the last poster in an unexpected way that still make sense and then post your own prophecy for the next player to fulfill for example:

Prophecy states the villain will only be defeated when the trees speak up against him.

The hero learns ventriloquism and uses his ability to convince the people to revolt. 

Prophecy states that an orphan will take the king's crown. How will this be fulfilled?