Wan Sum Dung is a Dung Beetle who loves to roll around in Dung. He requests that Salsa bring him dung, something that is easy to do, as the Dung Beetles are no threat to Salsa, even at a low level. For each piece of Dung brought to him, he gives Salsa 5/10 or even 50 exp. Should a level up be gained by giving him Dung, all of Salsa's stats will go up by five, and this can easily be done by defeating other monsters. It's basically a win-win situation for Salsa, as he gets Experience from defeating the Dung Beetles and giving the Dung to Wan Sum Dung.
Wan Sum Dung's name is a play on words. He Wants Some Dung.