User blog comment:Mckrongs/Monster Hunter 4 for the Nintendo 3DS/@comment-1011548-20130917103937/@comment-17735225-20130917113210

There used to be 'pure' download exclusive monsters back in MHdos which are the rare species of raths. Their data doesn't even exist in the original game disc and must be download from the server.

But since quests like these never appear in any later games (DLC quests are already in the game, just need unlock code) I doubt  there will be in MH4.