.....and how did the table turns?
spoilers
that's just one part of it. That's what caused emperor to become possessive (remember back in ch 17, I think, when he said an emperor can just seize whatever their heart desires & make it theirs by force). The brutality is caused by another factor that is not yet revealed. To put it simply, this emperor is born with a very rare & unique genetic trait. That's what contributed to his extreme brutality, since he just simply didn't know the extreme pain that resulted from his torture was actually a horrendous thing. he really just didn't know, & he had no means to understand it back then, up until that moment when he cried seeing Heun so deep in his addiction and then eventually died. Only then he started to learn. It's very sad, really.
KYUNGSOO IS SO FREAKING ADORABLE!!! CHOWON U ONE LUCKY ASS BETTER TREAT HIM RIGHT