Rui Fei's Jenga strategy

But because it feared what this strange boy with hair that flowed down like mercury would do to that eye it gathered all its strength and swiftly changed into a black fog to make its escape.

Rui Fei wasn't at all surprised, in fact, he expected it. It's just that he enjoyed the feeling of giving this creature hope.

Imagine a deer being chased through the forest suddenly getting the feeling that it had escaped from the clutches of death only to be delivered a final blow out of nowhere. It was the sheer disappointment and agony that stems from it that intrigued him. This is why he couldn't help himself but toy with his prey. 

The creature that thought it had escaped death continued to flee but before it got far it was suddenly grasped by a dark power and ruthlessly slammed to the ground reverting to its true form.