Honestly the major part of the drama was absolutely perfect but then it slightly toned down at episode 10 when the characters started shifting loyalties and joining other sides.
The characters were amazingly written with majority of them being in the grey zone and being neither fully bad or good. My favourite one would be definitely Gu Reum, I really liked how she was strong both mentally and physically and was an icon. My most hated character would probably be the spiritual leader of director Kim and the actors did such a great job with playing these villains.
The OST was catchy but the English part of the lyrics weren't making much sense tbh...
I feel like the ending left us with some unanswered questions and although I don't have any hope for second season to happen, I still wish for it.