Mythical Monster Hunt is the Halloween event. It progresses quickly during the early ranks, but slows down massively towards the end. It cannot be completed with a reasonable amount of spending, and Rank 30 alone takes multiple days with the four best rares at level 6. Wave missions are the most difficult the most often, with Groves becoming difficult towards the end. Most Sandstone, Statute, and population missions are easy, if not completed as soon as they show up.