Aramintai

Some soul ejectors may have been from some old stash from that 200 year old war. Shaman's family held a grudge since those times and kept that forbidden book, they may have stashed some sorcery stuff from those times.
Or, since we're talking about ML's father here - he was the one experimenting with the ice stone. Yea, shaman got her hands on it 10 years later after he sealed it away. But at that specific time he had it and he had soul ejectors as well, he used one to get himself back to his body. So he probably knew how to make them from the ice stone as well. And again, all those guys were in cohoots back at that time.
So I'm betting on the latter - it was all ML father's fault, no continuity problems here.

It wasn't explained.
I'm thinking it got something to do with ML's constellation map. ML's failure of a father wanted to hide it, so it may not be unreasonable to think that he himself or one of his underlings soul shifted into FL's father to do the switcheroo and then soul shifted back. And we've all seen that ML's father was still a soul shifter - even if you return to your own body after a soul shift you're still a soul shifter apparently.
And even though ML's father mourned FL's father as a friend, you gotta keep in mind that he was experimenting aos on his associates at that time, at least 8 of them ended up petrified in the lake.
And Jin Mu worked under ML's father at that time, so everything he did was likely under his supervision, their goals aligned back then. They parted ways only after ML's father got cold feet after his son's birth.
The question remains why ML's father would need to soul shift FL's father if they were friends. But it is a good way of getting rid of someone who knows too much without dirtying your own hands - make him a soul shifter who runs wild.

He's out there, knowing everything and doing nothing as usual.

Why three years gap though?

I hate mama Jin, she doesn't deserve to get Bu-Yeon back. Not only is she the dumbest, densest character in the whole drama, she's also a big fat hypocrite when it concerns the ice stone. And her obsession with Bu-Yeon ruined her family. And though papa Jin's fate was poetic in a way, I feel sorry for neglected Jin Cho-Yeon.

No happy ending? Who died? ML's daughter?

Let's hope it's just your typical misdirection for hype sake as they usually do in the previews. And that amnesia better be resolved fast. Judging by the teasers it will? After all, they usually tease stuff up to ~4 episodes.

Yea, and they look so damn fine in part 2 teasers, they better not AoS any of them again.

Yea, hold your pitchfork and torch at the ready 😠

I think one lead getting a body swap is controversial enough as it is, if both of them end up in different bodies it would be a massive offputting wtf. But who knows, you can't trust Hong sisters...

If part 2 won't have a happy ending neither I'm gonna riot (╯°□°)╯︵ ┻━┻

Is he similar to Bu-Yeon now? She also wasn't supposed to live and was birthed with the ice stone's help.
Or will they have to AoS his soul into another body at the end?
Implications are unpleasant.
😬😨

Also, whatever is going on with Yul is giving me bad vibes, he may very well go down like many a SMLs in romantic saeguks.

Why are you wasting time here writing walls of text instead of simply watching it to write an informed opinion after? It is incomplete right now, watch at least few more episodes 🙄. Everyone's tastes are different, no matter what people say here, it will not change your own opinion.

One more teaser:
https://www.youtube.com/watch?v=s1uMBo21SAI

And they didn't forget about the tree! They'd better get up there at some point, it's a must!

I disagree about FL needing much character development here, as she was already a nice person who was faced with dire, deathly problem. All she needed was to grow some balls aka. courage and thick skin to achieve her dream and she did it by having plenty of practice with ML 😂. And early episodes with her were great, they did show her going through famous five stages of grief, seriously contemplating her circumstance and having a profound revelation at the end. Then came that resolutional plot twist at the end of episode 7, her predisposition towards ML changed and the plot started focusing on ML's character development more. I'd say this drama is structured well.

That's mages uniform. And also, Daeho fashion.

I dunno, watch it again then? FL's frustrations and antagonistic behavior towards ML in the first third of this drama were very understandable to me. After all, she was told she's gonna die soon and there is a saying that stress is the cause of all disease. And it's not like she was the sole receiver of his nasty temper - there's a whole ex-secretaries club after all. And his other workers were absolutely terrified of him as well.
And she didn't hurt him with that hammer or ran him over with a car, did she? Her revenge was mainly petty pranks. And I wrote above that you'll see her kind character even in her revenge bouts. Just keep watching.

And this drama doesn't rush character exposition, but doses it expertly through the episodes. And both leads undergo great character development here. But again, if you can't tolerate this drama's characters - drop it.

1. There's ML's ex from 12 years ago, she's is one of the antagonists, but he's very negative towards her and never shows interest in getting back together.
2. They start dating in episode 12.
3. There's no breakup.

Alright, I'm not gonna read all of that giant wall of text. But in short, FL's health problems were due to severe stress at work, after she learnt that she has nothing to lose she stopped putting up with ML's bs and her headaches got better after a while. I guess revenge is a good stress reliever and also there's a plot twist about her illness in episode 7.
As for her personality, she's an introvert and generally is a timid scaredy cat. Her friend and family mentioned she's usually very kind and won't hurt a fly. And you can see that even in her quirky revenge on ML - how she spent his money on charities, helped other workers at Gotop, made ML reconcile with other people, etc.
Because of her stage fright she failed her initial instructor audition, but as the drama progresses she gradually starts having a different look on life after several revelations and finds newfound courage to pursue her dream in earnest. If you keep watching, you'll see how she achieves it. But if you don't like FL so much to write such a detailed wall of complaints then just drop this drama.

At this point are they even gonna do a proper Kang Chae Ri's background exposition? What's up with these half assed, spoon fed hints about her family history? Without full context her behavior just looks like some weird randomness, especially what she did in episode 14.
What's up with her? Her mother died and she has a bitch stepmother who hates her? Or what?

As for the other couples, OTP couple consistently stays boring and unconvincing. Also, that was the most kdrama style of falling from a building, how the ef she managed to fall, while drunk bitch landed safely on the balcony? 🤦‍♂️😂
Props to Han Ji Yun for feeding ML's face with a cake, about time she grew some self esteem.
The only couple I'm still mildly interested in is the chef and the webtoon artist, but it's unclear if anything pans out with between them.