It was so rare to have such a thing, and it was kind of like what Berry suffered from when William first met her. Yet unlike Berry, there was no future hope for any of the Mutants.
Their spirits clashed against each other for the rest of their lives. Yet as there was a grand difference between the two spirits in terms of quality and grade, it was easy to overcome and control such clashes.
William wanted to aim towards this. And to do so, he got to find something that could stir up the spirits within oneself.
Such an item wasn't rare actually, but that was the case in the outer world. As masters there needed a stimulus sometimes to grow their spirits stronger and fiercer, to overcome any stagnation in rising one's spirit power up, they used such methods to deal with these problems.