I once played in a fey-heavy campaign. At one point we were hired by a an unseelie noble to murder his half-fey son. We didn't want to kill some random guy so but we also didn't want to flat out say no having dealt with his type in the past. We politely asked if he had any other job for us. He said it was either murder his son, be his servant for 100 and a half years, or he would kill the prettiest member of our party. We understood that if we didnt accept one of his offers we would all die. We accepted the first offer after being assured that our payment would be fair. We did the deed. Turned out his son was a changeling (mythological sort) and was left as the child of a king. We were now the most wanted criminals in a powerful nation. We returned to our hometown to stock up on supplies before collecting our reward. This is whe we found out one of the PCs son had been killed. Fair payment indeed.

It was a very fun campaign, we quickly learned the only way to survive dealings with the fey was to pit them against one another rather than us. Also never say the words "thank you" because fey see that as the ultimate form of ingratitude, you show thanks with favors not words. Oh and don't tell them your name, that's how I got mine stolen. Nobody could remember what to call me and I had no recollection of my own, in the end I traded the color of my eyes to get it back...
Like I said: fun campaign