This drama had huge potential. Right from the start, it was an interesting watch that viewers would easily get hook by the mystery of the unknown world. However, I just can't seem to feel the main leads' chemistry, leading me to frustrations over their undying wish to save each other. Sometimes, I even wish to see the two of them die because their lovey dovey scenes didn't work to me. That part of the plot ruined the drama for me. For the thriller and action parts, it was interesting and for most part, I've enjoyed it. For the characters, I really liked Nam Ji Ah in the beginning but as the story unfolds, I grew to dislike her for being a nuisance for almost everyone. I also have to admit, my favorite part was when every time the Imoogi comes out of her, Jo Bo Ah nailed it. Everything else was okay, I can overlook minor issues along the way. However, here comes the ending. Lee Rang was already happy and contented but why did they choose to kill his character? I thought they would do something about it. It frustrates me just by thinking that when one main character dies, everyone would do anything but when a side character dies unnecessarily, it's okay for all. I mean for other cases, it would be okay for me too but that was sudden and felt unnecessary. I'd rather choose an ending where the leads got to reincarnate and meet again or a cliffhanger, because I've already prepared myself at the beginning. Anyways, I have mixed feelings with this drama. Maybe people who are only after the action, thrillers or legends, would enjoy this, but I will not recommend it openly to friends who would want to watch a drama of the same genre.