This review is way too long, but I have a lot of thoughts.
The first 25ish episodes were fantastic! They were compelling, twisty, and smart with morally grey and interesting characters. There were several times that I stayed up too late because the plot took off and I had to see how the Emperor was going to get out of the trap laid for him.
But then we hit a lull and for like 15 episodes Qi Yan was suddenly sidelined because he got stabbed like 5 times and was apparently dying. He moped around in his flowy red robe like an ailing Victorian child practically the whole time. Not only that, but for these stretch of episodes he seemed to get kinda dumb (as in: his plans weren't well thought out and he was being fooled by everyone else), which really undermined the character he was presented to be at the start of the show.
Also, I'm not sure I understood why he was dying. Maybe it was the translation, but when the doctor was like, "You may die in five months or five YEARS," I was lost. I don't understand the huge time gap there. I thought he was only stabbed? Did it get infected? Was it poisoned? Am I actually too stupid to follow what was going on?
It was at this point that I started to skip because they felt like filler episodes. But I kept going because I was already invested in the plot and the characters.
The romance didn't really work for me, but I didn't hate it. I just thought they had no chemistry, and no offense to the FL, but I didn't think the actor fit the the part or played it well.
The Duke was a good villain (I think this is due to the actor), but there were times that it felt like he wasn't as smart as we thought and was mostly just lucky and too firmly rooted in his position to give it up easily. I also wish that he and Qi Yan had more time to stew with each other. I wanted to know more about their relationship before it went sour. Also! Completely unrelated, but when the Duke goes feral at the end and whips off his robes and his hair goes crazy, I died laughing. Which I'm sure wasn't the intended reaction.
Lastly, I'm not sure what to think of the ending. There seems to be some confusion about whether Qi Yan is alive or not. To be honest, I assumed that he'd faked his death, but we didn't really get that much of a confirmation, so I'm not sure. But in either case (him dying or pretending to fake his death to live as an ordinary person), I don't really like it. I know that he didn't want to be Emperor and it brought him nothing but pain, but at the same time it felt a little cheap for the audience to sit through almost 50 episodes of him STRUGGLING to hold onto the throne only to give it up (or die) in the end.
I'm complaining a lot, but I actually really liked this drama. It's one of the few cdramas to hook my attention and hold it through almost the whole thing. I tend to give up somewhere in the middle, so the fact that I finished this is amazing for me. Which really speaks to the plot and characters of this drama. I just wish that the fat had been trimmed story wise and that the Emperor had actually been allowed to be the MAIN character throughout the whole thing.