So, it's a story with three main characters who are the driving force behind the plot.

Park Gye Won
- is a powerful prime minister who overthrew one king, installed another, and is currently trying to make the newest king his puppet

Lee Tae
- is a young king
- after realizing how powerless kings are compared to the ministers, he's trying to strengthen royal authority and solidify his own power
- is in love with Yoo Jung

Yoo Jung
- is a daughter of a scholar
- as a teenager she was selected to be the crown princess but her family got accused of treason and annihilated
- she, however, was saved by Lee Tae (then crown prince) and they continued seeing each other for years without her being aware of his real identity
-years later she involuntarily got involved with Park Gye Won and came to court where she became one of Lee Tae's concubines

What this drama has:

1. Impeccable cinematography.
2. Beautiful soundtrack & gorgeous costumes.
3. Good story that combines politics and romance and nicely incorporates romance into the political plot which adds to its significance even though it's not the main focus of the drama.
4. Interesting and well-developed characters that can't be painted as good or evil. They all have their own ambitions and ideologies that are justified and completely reasonable when you look at things from their perspective. It's one of the things I love the most about this drama. In the power struggle between the young and powerless king who just inherited throne from his father, who was basically a puppet king, and the experienced and influential minister who controls the court, the king is cunning and the minister is not power-hungry for the sake of his own ambition. Add a strong and smart female lead, who has connections to both male characters and who is not overbearing but acts within her social confines, and you'll get a really interesting story. Characters who are enemies but can form compromises, change their allegiances and go against their loved ones to achieve higher goals.
6. Amazing acting from all leads. Jang Hyuk who plays the minister was expectedly good, but Lee Joon who plays the king was a revelation for me. The way he balanced between the cunning, ice cold/ruthless king and the king who is worried about his loved one was really good. His often teary eyes were a nice bonus and they showed how constantly anxious, worried and angry he was. Kang Han Na who plays the concubine also managed to successfully portray all the complexities of this character. She exuded such dignity!
7. Good pacing. Every episode is gripping and keeps you wondering about what's going to happen next and how are characters going to react in given situations.
8. Satisfying ending.

What it doesn't have:

1. Action/fighting scenes. I guess it's one thing that people who love historical dramas may find lacking. There are some fighting scenes but they are few and far between. This drama is heavily focused on court politics so it's not something unexpected.
2. The political plot gets a bit convoluted towards the ending and some thing don't make much sense (to me) but I don't know much about the real historical context (what was possible and what wasn't possible at Joseon court) so I tried not to let it affect my overall score.

I honestly don't understand the reason for the relatively low MDL rating. I would recommend this to everyone who loves sageuks, especially more serious ones.