The black, crystal-like stone in Magus Xion's hand was exactly the stone he took from Morgana, which meant it was the one who originated from the now dead witch, Meave.
When Magus Xion asked about the origin of power that came from the stone, there was only one answer that came into his mind. The Khaos energy.
However, in order to be sure about it, Emery decided to carefully probe the question.
"What do you mean, Master?"
Magus Xion seemed to become more restless when he heard Emery's answer. Seeing how the usually calm master of his became uneasy, Emery became even more curious about the significance of the stone.
All will be revealed next chapter