I'm sure everyone has played a version of this before, basic story game. I say a sentence, next poster adds another sentence and so on. One minor difference is that unless it gets to big to post ADD your sentence to the existing sentence, as opposed to posting only a new sentence, that way there's a cohesive (lol) story at the end.
post 4 for example would look like : Sentence 1, 2, 3, and 4.

The wind whistled through the canyon, chilling the poor young man to his very bones, as he strode out of the darkness.