I watched it because it had so much good ratings. What a disappointment.
The story begins with a plot that is classical and plain. There is the overused trope of fate and as soon as Eun Tak meets the Goblin the love story is forebode. But that's okay, it's well done and their firts encounters with both of them searching any interest in a potential relation is interesting ( she wants to use him to escape her life while he wants to use her to die ).

However, it does not get better.
The rythm is too slow, and the side love story between the Gream Reaper and the shop owner is boring and useless.

Even the bromance is not that good. The transition between being ennemies to friends is not smooth.

The whole stuff of reincarnations is so bad as well. Kim shin is shown as a bright man ( he won a lot of battles because of physical strengh but also by strategical means ) yet he does not make the difference between his sister and her new life ??
Furthermore at the end every reincarnated people have the same face as their previous life body, yet it had been specified that people randomly reincarnate into different bodies and having the same is rare.
The backstory of the medieval plot is thin as well and the characters are not fully developped.

The final fight with the main ennemy is failed as it is teased for some episodes ( and visually he is scary and charismatic, his dark tongue gives goosebumps ). But why is he killed with almost no fight ?? Kim Shin awaited more than 1000 years for 30min of dodging ??

And the 3 last episodes, a disaster.
Kim shin finally dying wassad but actually it was a logical ending : he was released from his suffering and allowed to live happily by embracing love at the very end of his existance. Eun Tak would cherish her memories of him and mourn him knowing that he left peacefully.
Making her die at his place is such a nonsense. First she embodied the future as the younger character. Second, it means that Kim Shin will never die, and that it was a punishment of god ( rather than a way to relieve him from his pains ). Not only did he suffer for years because of the betrayal of the King, but now he has to eternally suffer from the lost of his wife. What is the moral of that ? "No matter what you do to repent you will suffer ?" It does not make sense since we know that the sinner is the Grim Reaper and not Kim Shin.

On the whole it is not the worse drama ever, but it lacks in many points. It is still fully watchable, the characters are attaching, and the fate of the Goblin is touching : we want to know how he will find some happiness.