Rank-up missions were what allowed one to advance to the next tier of levels. For me, to go from level 9 to 10, it was getting the Primordial Villain class and a few other criteria, but according to the system message I got, I wouldn't have it easy next time around, as supposedly primordials have specific trials they need to overcome, but for some reason, I had it easy with the first one.
Just for reference, Aurora's mission was to negate a certain amount of damage incurred with her shields and buff us up to deal a certain amount of bonus damage due to her spells, as well as concoct a few potions, but she'd already achieved that a long ago. Her Enchanter class was truly starting to shine with each level, as she went from a simple shieldbot to an all-around magical supporter, but of course, she had only basic spells at her disposal due to her low level.
