Since _pouf_ is not a proper noun and has no reason for quotation or capitalization, [the most proper form](http://english.stackexchange.com/questions/50412/what-is-the-proper-convention-for-writing-onomatopoeia) would be "From the south, you hear a pouf!"

Honestly though, the game is rife with other examples of poor English which are more worthy of scrutiny (the "its-or-it's" mistake is particularly rampant).