So you know, the remaining character should be Ellie, who is from the rest of the Marl Kingdom series. She also shows up in the Rosenqueen store and implies that she's an erynga in human form, since she tends to go "eri~" like they do. She's pretty much the easiest DLC character to get gamewise, while Hero Prinny, who is also free, is level 100, last I checked. The other two cost money, officially.