From the beginning, Grey had noticed that the purple crystal could suppress all life forms under it. It's supressive might was so strong that nothing under it's light could put up a fight.
Not only that, Grey noticed that the purple crystal was also very possessive. Ever since he obtained the purple crystal, it had slowly been changing his body and his internal world.
Such that his sea of consciousness was dyed slightly purple, the Soul Devouring Bird that a partial emperor level cultivation art was also influenced and turned purple.
His other arts and techniques were also influenced by the purple crystal and turned purple. They each also had the same supressive tendencies as the purple crystal. Especially his purple moon.
And if the purple crystal could influence even a emperor level cultivation art, even if it was an incomplete one, then it was clearly a supreme item.
