Mission 1; Get Lucy/ Natsu and His Motion Sickness!

When the "most powerful team in Fairy tail" get a job that asks for a extermination of "the demon of death" with 200,000 jewels as an offering, it's obvious the quest is a S-class, yet why was it on the normal quest board and more importantly, why would they order the death of one thing that does no harm to their town?