This series falls into the well-known k-drama category of fantasy with elements of religious myths and tales, so if this is your thing you will probably quite enjoy the ride. Starring established actor Lee Seung Gi, it was actually the first work of his that I ever watched and his acting was a revelation for me, as well as, I feel like, one of the main selling points of the drama. The plotline starts off very promising and develops quite naturally as the episodes pass, keeping you invested and guessing 'till the very end, which is something I quite appreciate in dramas like this. The main romance doesn't feel forced and the relationships between the characters actually seem realistic, despite them actually belonging in a fantasy realm.
The only problem I had, really, with this drama is the length of it. I feel like 20 episodes is a lot, considering the story felt like it was dragging a little after the first half and featured a few unnecessary parts, in my opinion. Also, I have to say that the main actress, though quite looking the part, felt a bit stiff to me, especially when unavoidably comparing her acting to Lee Seung Gi's.
Overall, I quite liked the series, the production was very well done and the plot is worth a watch, though I wouldn't include it to my list of favourites ever.