Bulgasal was the fantasy kdrama I hoped would end up on my fave list. It had everything, a never explored mythical monster, it was immortal with limited strength, not ridiculously invincible and no additional superpowers like tracking down your enemy with psychic powers or something, I loved the explanation for immortality. There were several motives for revenge for several characters. Also, there were additional monsters like Yeongno, Gapsangoe, Teoreokson, etc.

I watch all my shows with some speed acceleration be it 1.15X or 2X, I didn't do it for this one. That much I was drawn by this show. I couldn't drop it either because of getting myself invested in the badly written but likable characters along with ML's and SML's amazing dynamics. I have rated low for the story not because it was that bad, but I had so much higher expectations. I don't regret watching the show and on a second chance, I wouldn't stop my past-me from watching this.

Story: I would have just watched the first 4 episodes and the last 4 episodes and be done with it. Aside from these great start and ending, the show was badly written in the middle and I was constantly expecting it to give me answers till they kept dragging it until the penultimate episode.
This had the style of soap rather than a series with its pacing and can easily drag for 20 more episodes. There will be new tiny twists and revelations for each episode just to heighten the emotional impact and (un)necessary hurts, kidnaps, and deaths just for the cliffhanger effect. Maybe, I would have liked this style, had I not binged in a week.
The house hopping didn't help either. I mean if you are planning to hide from someone, then hide and stay hidden until matter subsides but, no, they will be going from A house to B house and back to A house. They ran out of budget to shoot in B house and/or was sort of vacation-type filler content.
This was the only time in a fantasy show I saw people relaxedly eating and doing laundry more than actually fighting and making up decent plans. Heck, now whenever I'll dry laundry, I'll remember bulgasal getting lectured on drying laundry. (Sigh)

Predictability: After watching some 300 plus shows, and all kinds of fantasy shows, the predictability factor becomes moot. That being said, this show was decent with its twists, I wasn't surprised nor disappointed. I saw the twists coming but it wasn't bad.

Characters: I felt they were certain logical inconsistencies in why someone behaves in some way. There is a character who got bored and couldn't watch tv while being in hiding from the bad guys so says let's go and be with others. And one thing leads to another and she ends up straight in the devil's lair and dead. That just sums up all the character rational moves. Every death of any character was utter stupidity of themselves or others. So I could barely sympathize with any of the characters' death. In retrospection, I would call this show more in a lighter mood than angsty. (Coping mechanism, to not cry?!)

Cinematography: I liked the wallpaper-worthy scenic locations and camera shots especially the flower shots in the background and the top view shot of bulgasal having his drink by the waterside, the birthing scene and the beautifully shot 600-year segment. Even if half of the effort given for the locations and cinematography, had been given to actual story writing, then it would have been so much better.

Music: I loved the intro title theme music and the intro credits montage was so good. Ost was good. My top three would be Janet Suhh's Beyond The Time, Minseo's Can't Forget You, and 4Men's One Day. They all made me feel the eternal vibe of the drama which it was exuding. The only downside was the grunting roar sounds felt random. They don't seem to make any lip/body action syncing to it.

Fight scenes: they had decent camera work, older kdramas had shaky cameras for fight scenes, and boy, they have come a long way. The fight scenes of ML were pretty decent and others' fights were not so. Action isn't the show's main focus. I liked the color of fake blood and how realistic it looked, and eye color change, with long nails, skin darkening it was nice.

Revenge: 90% of the time I was like where's the revenge? Where is it? If it was the 2 episode arc of each monster then it was okayish. The writer wanted to include the monsters even in the 16th episode. Then least give them a better backstory and good past scenes instead of a one-line description of what they specialize in. I was very invested in these monsters and their nature. Though they could have been gruesome and not some simpleton psychopaths. (Intended to be light-hearted?!)
As for main revenge? who is the baddie? That search itself gets draggy and even if they find it, this has hardly the revenge drama I expected it to be. Nevertheless, I liked the ending fight scene and prophecy coming true part, and whole bloodthirstiness, and the take on humanity. It is sad and bittersweet that despite being immortal, nobody wants to be immortal again.

Acting: I liked the acting of all the actors especially Lee Jin Wook, he was so perfect for the role, he had a mysterious aura, a good guy vibe, demonic vibes all rolled into one. In my opinion, his present-day hairstyle was so out of trend and he has a similar hairstyle for the 1000 year flashback as well. But he looked great in the 600-year segment.
As for Kwon Nara, first time seeing her in the main role after Itaewon Class and Suspicious Partner. She has often played annoying characters, I initially hated her character here as well, but she becomes likable after time progresses, her character was the softest of all. She falls badly whenever she gets slapped was so awful to watch. She looks so amazing in past scenes with the long flowing dress and hair but her present-day look feels like she will fly away with the wind. Her face looks weird in the present-day segment or is that her neck is elongated.
About Lee Joon, first time seeing him, but wow, so smitten by his acting especially, his dejected look for getting rejected, and the pained scenes. Man, I can't hate his character with the way he portrayed it.

Romance: I so didn't want this to be romance. Because this was touted to be a revenge drama. The posters and other things didn't give any romantic vibe at all. Even if it existed it would be with the wife, I had expected. I had a hard time adapting to seeing FL in that way as she is introduced to antagonize even though she is attracted to ML very early on. Maybe the writer changed their mind halfway through drama or it wouldn't be a kdrama if the ML doesn't romance with FL. They could have given hints from early on that there will be romance. I kept wondering where is all this strong love coming from? And the only kiss was CPR kiss, what was that? Despite this, I kinda liked the romance because it felt unconventional. In my perspective, I wouldn't think of this as forced romance as it becomes essential to understand Bulgasal and its obsession. Bromance was written better. With SML actor pained looks and ML saying sorry, woah amazing.

Ending: I was infinitely happy with the ending which wasn't bittersweet, in my opinion. Usually, I hate time jump ending but this was so perfect. I couldn't calm myself down all night.

Euphoria-like happiness sort of emotion is rare for me as the only reason I watch dramas are to feel happy and this show did it for me despite not having good writing, smart characters, and great romance. And I'm still wondering why I like this show and why it made me happy.

Bulgasal: Immortal Souls - but it will be immortal in my heart.

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Extras: (Can contain spoilers)

Lore: Personally, I didn't feel the need to know more about the origins of bulgasal, as it would miss that folklore-y feel. Also, about the ending reincarnations, it is a gray zone. Hwal's words aren't surety, as he wasn't talking from his experiences or other extinct bulgasals. No one knows what happened to extinct bulgasals. As for Min Sang Un, she was an anomaly as the eighth reincarnation gets split into two souls likely resetting her cycle.

Characters portrayal:

Almost all characters have a certain level of slow-wittedness inherent in them. In this sense, I would not be criticizing them harshly and taking the drama lightly.

Dan Hwal was constantly driven by his prejudices and pre-conceived notions, but easy to understand others' views when given an opportunity. He is easily the most complex character and difficult to judge, I kinda understand him without judgments, why he was in a certain way in the 1000 years, in 600 years, and present day. I feel mixed emotions of love and disdain for him. Also, he was easily driven by others' views. It must suck to realize that you had been working for the wrong goals for so many years.

Min Sang Un was truly the saintess of kindness in a world of psychopaths hunting for her. As a child, she was not at all trusting her twin which felt weird. As she grows, she has better sense and she wasn't completely trusting everyone, but sometimes, she still did take stupid decisions. I kinda understand why she is the way she is as the story progresses and the 1000 year flashback made it clearer. I won't criticize her for falling for ML as it was more of an instinctive choice in retrospection.

Ok Eul Tae was the meatier character of three main roles. He was more humanly sometimes and I liked his principle of not hurting until necessary. I couldn't hate him at all maybe except when he was a human. He was the smartest of all, given how he becomes bulgasal, smartly handles every situation, and even adapted well to the present day. He was truly the guy who won't go down without putting up a fight. Also, his dynamics with Hwal were such a treat to watch.
Min Shi Ho was initially don't care attitude, but later on, she cares for others, but she still loved her sister the most. I liked that she was most skeptical of Hwal.
Nam Do Yoon was the eye candy. He was the best of the squad. He could have had a better ending in the time jump scenes. His scenes were just too hearty and funny to watch his interactions with Hwal.