In the beginning, Shane was astonished by the quick change of the subject which the Emperor addressed.
However, after thinking about it for a short while he realized that it was only logical why the Emperor wanted to see his strength.
The Emperor had only thought of Shane as a mere pawn until now. But, after hearing that his race would be able to claim multiple elemental crystal caves in a basic dimension and the possibility to get the exclusive trading right with the human race, Shane's importance drastically increased in his eyes.
The Emperor was already glad to have received so many elemental crystals from Shane but it was still far from enough to have a stable supply for future generations!
As such, having an elemental crystal cave or the exclusive rights to receive elemental crystals would solve this issue, allowing them to expand in the basic dimensions!