Queen Munjeong (my profile pic lol) is THAT bish, literally overshadowed everyone at times - All hail Jeon In Hwa. Kyungbin and her attendant Geum also had a really interesting relationship - I also feel like this drama had a lot of love hidden under the name of "loyalty". Like, Nanjung and the Queen were *totally* just political partners... that plan to go live together, trust each other on everything, would die for each other, give birth on the same day, promise to never throw each other away... yeah, *just* friends.
I also enjoyed Nanjungs gisaeng friend Maehyang - cuz it just showed how oppurtunistic she was (plus Park Joomi is gorgeous). Attendant Uhm was absolutely iconic too!