Finally it’s actually fairly easy to solo this challenge. I guess if you have at least 5500 magic/spirit/physical attack it can easily be done on your own. The exception to this is Elpintos, Nagi & Cromodo. Cromodo simply because he just gets knocked around too much and Elpintos & Nagi ….well Elpintos and Nagi （ಠ_ಠ）. The exp book from this challenge gives you about 38k. Pretty nice to solo and level up sub characters. Took me about 10 minutes per run.