Please pitch me your favorite historical drama (or any that you think apply)

The Princess'Man.

Six flying dragons. 

Haechi (historical but the main character is not morally ambiguous)

A modern, one with an ambiguous main character could be The Guardians (or Lookout)

I think "Legend of concubine Zhen Huan" fits totally. 

The story takes place during Qing Dynasty and tells the tale of Zhen Huan, a young noble woman who was married to the emperor, and for survive in the palace need to use the art of manipulation with a lot of agility. She switched between kind hearted and naive woman to a power hungry person. 

The palace is a dangerous and cold place where people are easily distorted and the enemy is not necessarily where you think. I heard the drama receive some criticisms because the heroin use the same tricks as the antagonists and it blackens her morality.

I specially like the moment filmed outside of the palace, as a dream, but it couldn't last.

I heard also some people in China use this for work their way up in their job. As for me it helps me to understand what behaviour can be dangerous in the work place.

Here the link, hope it can please you ;)

 https://kisskh.at/4474-legend-of-concubine-zhen-huan

Shine or Go Crazy. Three great performances from the leads Jang Hyuk, Oh Yeon Seo and Lee Ha Nui (Honey Lee). It's kind of a romance and political thriller about an early Korean kingdom, the Goryeo dynasty and the establishment of a famous king (a real historical figure, the story about coming to power is not historical). 

None of the main characters are passive. They all have agendas. Jang Hyuk kind of has that deep voice, a stage-like presence in the TV show. Oh Yeon Seo is the head of a merchant company that travels Eastern Asia doing business and Lee Ha Nui is a noble woman who is ruthless at playing court politics to get her husband or her brother made King.

There are a few things that were kind of a bit silly like one of the characters pretending to be a man and not getting recognized but other than that I loved the different characters all playing their angles especially Lee Ha Nui.

I know it's got a low rating on here and a lot of people didn't like it and gave up on it... but it's worth giving a chance and going through the first 3-4 episodes. It was one of the highest rated Korean dramas at the time it aired and it got 24 episodes (as opposed to 20 or under which is typical).