@Prinzinc my guess is it's going to proceed like this. He finds out using the people inside of him skills and letting them take over damages his body, or leaves him weak. So he has to learn to use their power on his own and strengthen himself in order to teach his potential. Also it seems like his crest of nothingness just meant he a huge reserve of power, but no conduit to produce it. Leading me to believe that he will surpass all his masters in their own skills