This review contains spoilers, as well as some slightly inflammatory opinions.

This drama made me very angry.
It didn't make me angry because it was that bad. On the contrary, it was so good it could be perfect - if not for the little things, at first, and the bigger ones later, that started to add up, until I couldn't ignore them anymore.

1. Casting and acting.  At least two of the main leads, Ha Ji Won and Ji Chang Wook, held up very well - I could rather call them exemplary. So did Kim Ji Han (Tal Tal) and Baek Jin Hee (Tanasili). I would actually say that the acting was very believable, if not for some over-dramatic moments that occured everytime a twist happened or new information was disclosed, but maybe that's common in "historical" dramas.

2. Music and costumes. The music was beautiful and well placed - except for, again, some over-dramatic drum banging. As for the costumes, their quality was good and I enjoyed seeing all that Yuan and Goryeo couture and skin routine. The choreography was also good, apart from the occasional kicks in the air and people falling without getting hit.

3. Story and characters. Now, this is what I had most trouble with. I'm pretty okay with watching period and pseudohistorical shows, but they've got to stay believable. If a writer really thought that women can give birth in a cave, with no support whatsoever, and are then able to go out and about shooting arrows, that writer outright insults my intelligence as a viewer. How can I take anything seriously after that? Not to mention the whole "curses and rabid dogs" storyline.
Extraordinary feats aside, the plot was dragged in the middle and then became too convoluted after 40 episodes. I'm actually pretty sure the only reason we saw about the vouchers was to satisfy anyone rooting for Wang Yoo - and I'd be fine with that, if only there were a more interesting setting. Never mind that, but after the first 40 episodes, the heroes' actions went from mildly thrilling to straight up unbelievable.

Which brings me to the worst part of my review, the characters. In my opinion, the characters weren't created with care and respected, at all. This has nothing to do with the historical aspect of the drama, as it concerns mostly minor characters. For example, Yeom Bi Soo, or else Batoru. Batoru had no agency, no personality. She could be such an interesting character, but was instead used as a plot tool, and a weak at that. Silk road? Bam! Vouchers? Bam! Convenient sacrifice? Bam! She essentialy existed to move the plot forward and had no other qualities. Also, after the 42nd episode, even the characters that were well-developed so far started falling apart. Nyang Ki goes from an intelligent and well-nuanced character to being the "bad guy" (as if we're suddenly watching this through the Dowager's POV), Ta Hwan takes 10 steps back on the maturity that we've seen growing in him, Kolta... don't get me started on Kolta. Kolta was the designated villain when it didn't even make sense - never in 47 episodes had we seen him express anything else but love and loyalty for the emperor, and then he makes a 180-degrees turn. Did that really happen? Is it a new addition? I don't really care, just build up to it through the episodes. I know it was meant to show that Ta Hwan couldn't trust anyone but Nyang, in the end, but the whole tragedy of it got lost down the drain. I think that's what happens when you only add conflict for the sake of conflict - I would have like to see more explanations, more of a background, but action got the better of it.

And let me get one more thing straight: when you continuously cut 5 years to the future, especially when there's a conflict unresolved, without much reason whatsoever, it's not good storytelling, it's a cop out.

That's all for a drama that I very much enjoyed watching but had many flaws as well. Extra points for badass Nyang, excellently executed conflicted Ta Hwan, and the last 2 scenes that brought me to tears.