@Snowflower asked this question in the other thread.

@pm3, I was also wondering if Jang Gang put another baby’s soul into baby Bu Yeon. Or is it possible that he summoned the soul of BY back into her own body? Either way, if BY is a soul-shifter, she should have gone wild. Why hasn’t she? (We are assuming that BY is the original blind Mu Deok and both BY and Naksu share BY’s body.)

My short answer:

Based on what we know as of Episode 12, the only answer I could think of is soul compatibility. The innocent soul is compatible with the infant’s body. There was no clash between the soul and body because it began from the beginning. Thus, no crack was form.

From Ep 1:

Jin Mu: Why do the bodies of soul shifters turn like rocks when they run wild?
Jang Gang: A crack forms when the bodies clash with the souls they carry, which causes them to lose energy. This is already the eight soul that has run wild. I guess I should stop shifting souls.

The Hong sisters may or may not explain their reason. If they don’t, then it’s a plothole.

Here’s my long answer:

A. Let’s do an accounting of all the AoS in the drama so far.

Here are AoS we’ve seen so far that were done on LIVE bodies:

1. the King who soul-shifted with Jang Gang
2. Mage Cho, the father of Naksu, who soul-shifted with ??
3. Naksu who soul-shifted with MuDeok
4. the spy inside Songrim who soul-shifted with ??
5. the Eunuch who soul-shifted with ??
6 Gilju who failed to soul-shift with Uk
7. Mage Kang who soul-shifted with his able-bodied helper
8. Lady Jin’s husband who has been soul-shifted with Shaman Choi’s sibling.

From Ep 11:

Eunuch: I am the only one in this palace who knows that you are Shaman Choi, despite residing in the Queen’s body. If I die, you will bring your sibling here from Jinyowon?

So far, there’s only one person in Jinyowon who knows about AoS. That’s Lady Jin’s husband. (Edited to add this in case it’s not clear: I’m assuming he is the sibling of Shaman Choi whom the Eunuch was talking about. Either Lady Jin knowingly married somebody from the Choi clan OR the man she married was switched with Shaman Choi’s sibling.)

So we have 8 characters so far who have gone through AoS. Did I miss anybody?

Then, we have these instances of souls being shifted into a DEAD body:

1. the son of the desperate mother in the opening scene,
2. the dead man whom the King was talking about

From Ep 1:

King: Not for too long. Just seven days. Let us switch bodies for just seven days. I heard you once gave a soul a dead man’s body and that it lived in that body for over half a year. I am a king protected by the skies, and you are the best mage in this land. So what is there to worry about? And after seven days, you can turn things back. You have mastered the ability to do something that only the best mages can do. Yet you are wasting your time shifting souls into dead bodies. Jang Gang. Give this king a different body.

NOTEWORTHY: According to the King, Jang Gang had only been experimenting with shifting souls into DEAD bodies. The King would have been the first AoS on a LIVE person.

3 to 7. the five other souls that had run wild. Jang Uk said a total of eight souls have run wild.

He didn’t mention Lady Jin’s AoS on BuYeong. Two possible reasons:

a. Maybe he was being discreet and keeping it secret even from his assistant Jin Mu as Lady Jin wasn’t supposed to be involved in forbidden sorcery/bad magic.
b. Maybe this is another one of the Hong sisters’ plotholes.

8. the spirit of Gwiju being shifted into the dead Sapsali by Master Lee

My comments:
a. Do dogs have souls? Or spirits? I think the Hong sisters believe they have souls.
b. Yes. Master Lee is the man Yeo Heom was referring to who perform AoS with Hwansu. I just want to make sure we’re on the same page. And that the Hong sisters won’t introduce another Master down the road.

9. and last but not least, the dead baby BuYeon of Lady Jin

Of all these soul-shifters, both dead and alive, three didn’t petrified.

1. the dead Sapsali dog.

In my opinion, it didn’t petrify because it was soul-shifted by the use of Master Lee’s Hwansu, not by the soul ejector. Master Lee called it from the vault – like Jesus calling Lazarus from the dead or something. And the soul agreed to come out.

2. Naksu in MuDeok’s body

3. BuYeon

Let me go over what I know about Naksu and BuYeon.

B. Naksu and the Great Soul

I’ve been waiting for Naksu to petrify since Episode 3. At first, I thought she wasn’t running wild because she was constantly in the company of Uk who was a great source of energy. His “gate of energy” was opened.

But as of Episode 12, I attribute her non-petrification to:

a. the Great Soul inhabiting MuDeok/BuYeon’s body
b. the compatibility of her soul in MuDeok/BuYeon’s body

It was Master Lee who called it the “Great Soul” so I’m merely copying him. Here’s his monologue in Episode 5.

Lee: (talking to the Sapsali dog) I would not have recognized her without your help since her soul has no malice. (talking to the sleeping Naksu/MuDeok) You will be better off dying in my hands than to run wild and be petrified.

He lifted his hand to strike her. But a glowing aura emanated from Naksu’s sleeping form, so he stopped. When I first watched this, I thought of two things:
a) Master Lee couldn’t have been referring to Naksu’s soul simply because Naksu’s soul – as an assassin – was full of malice, and b) the aura sensed danger and came out of sleeping body as a protective defense.

Lee: A great soul has shifted into this body.

He closed his hand and put it down. In response, the aura disappeared. Note: he called it the “Great Soul.”

Lee: She should have run wild by now, judging by how weak this body looks. How is she still fine?

To me now, this is a hint. Gilju disclosed to Uk and Naksu that the ice stone prevented a soul shifter from running wild but that the ice stone is in the possession of the Queen aka Danju.

Lee: (feeling her forehead) I feel no energy around her. Where did it all disappear to?

Then he sensed Uk behind him. They dueled and ended up fighting outside the hut, in the rain. MuDeok followed them outside. Uk shouted at her to run. But his shouts fell upon MuDeok’s deaf ears. She remained motionless. She was in a trance, like a shaman whose body had been possessed by a spirit.

Master Lee powered up again to strike her with the ball of energy. Uk rushed to her side to block off Master Lee’s attack. Uk waited for the blow, but it didn’t come. Master Lee had changed his mind again.

And MuDeok’s head then dropped onto Uk’s arm.

That’s the important point here. The Great Soul in MuDeok’s body powered down because Master Lee stopped threatening to strike down Uk and MuDeok. This meant that this Great Soul would protect not only one, but both of them.

The following morning, Naksu couldn’t remember a thing. By the way, this wasn’t the first time it happened. Read about it here. 

Lee: (curious) Do you not remember anything from last night?
Naksu: No.
Uk: You stood right there and watched us fight.
Naksu: I did what?
Lee: I guess you sleepwalk. I will get you medicinal herbs for that. Brew them and drink the tea.

Master Lee must have realized that:

1. another sentient being inside of Naksu/MuDeok was in control of the body. He called it the Great Soul.
2. whenever Uk or Naksu/MuDeok or Uk was in trouble, it would come out to defend them. I already wrote about it. READ it here.
3. this situation was unique.

Lee: (tells the dog) That soul shifter is special. There is a great soul dwelling inside that small body. Let us get to know her a bit.

C. BuYeon

As for BuYeon, here are the relevant scenes about her.

1. Lady Jin was the one to approach Jang Gang and begged him to do the forbidden sorcery.

From Ep 11: 

Lady Jin: I had her inside me for 13 months. I cannot let her go like this. I heard the ice stone has the power to bring back the souls of the dead.
Jang Gang: (not saying a word)
Lady Jin: (kneeling) Gwanju. Please help me.

Jang Gang agreed to do it because he was moved by her desperation. (Good intention is NOT enough!)

He used the power of the Soul Ejector to bring the dead baby back to life by summoning her soul. This is similar to Master Lee calling the soul of the Gwiju and shifting it into a dead Sapsali dog. Only Master Lee used his Hwansu skills, not the Soul Ejector.

2. Jang Gang picked an auspicious date for the birth of the death baby.

From Ep 11: 

Park Jin: It has been ten years since the accident. Although she could not see, she could feel energy and could control relics like no other. She was a very clever girl.
Lady Jin: Unlike other babies, it took her 13 months to come out into this world. She was born on the very day that Gwanju Jang Gang picked as a blessed day from the skies.
Park Jin: (his interest piqued) She was born exactly on the day that Jang Gang picked for you? Is it possible to choose the date and time of a baby’s birth?
Lady Jin: It just happened to match. (changing topic)

I wonder if he was such a good seer, how come he didn’t see the entanglement between Mage Cho’s daughter (who’s still unnamed, by the way. #GiveHerAName #PreciousToo), Jang Uk the King’s Star, and BuYeong.

From oldest to youngest: Mage Cho’s daughter (aka Naksu), BuYeon, and Uk.

3. Reflecting on all of this, Lady Jin was determined to get her daughter back again.

Looking at Buyeon’s portrait, she vowed, “I went far and beyond to protect my baby. I will find you. I will do everything I can to find you.”

I think “by far and beyond” she meant that she engaged in forbidden sorcery to protect her dead baby in her womb. But I wonder why she kept the dead baby in for 13 months. Is that significant?

4. In my opinion, Lady Jin failed to see her child in MuDeok’s body because she’s been fixated on four distinctive features of BuYeon, namely,

a) she’s blind,
b) she can detect energy,
c) she can open the door of Jinyowon, and
c) she has an eye mask made by her.

From Ep 9:

Husband: I am back. I found her on a volcanic island in the south. She lost her parent at a young age, so she has no memories of them.
Lady Jin: She seems old enough to be BuYeon. Is there anything you have had ever since you were a small child?
Girl: (shook her head)
Husband: Unlike BuYeon, she cannot detect energy, and she does not know how to cast any spells.
Lady Jin: Maybe she lost her powers while she was away from Jinyowon. But if she is truly a member of the Jin family, her powers will easily come back to her.

Thus, when Naksu-in-MuDeok’s-body arrived at the Jinyowon, she didn’t recognize her long-lost daughter, despite the birds being agitated by her presence. I guess she should have used her heart to see. Lol. According to the conceit of this drama (conceit = trope, theme), it’s only with the heart that one can see the truth. Lady Jin wasn’t seeing with her heart.

But to be fair, she had no way of knowing that Naksu was able to open the vault with a single touch. She also couldn’t have known that Naksu could suddenly detect energy. She could see broken jade ball inside the box. When she stepped inside the Jinyowon, she experienced vertigo. It was as if she was being DRAWN to the vault. I mentioned before that like attracts like. The energy coming from MuDeok’s sleeping body in Episode 5 is the same energy coming out of the relics. Their energies are from a similar source: the ice stone. Since the energies are alike, they’re “drawn” to each other.

5. Buyeon DIED in the Lake but was returned to her soul.

From Ep 9:

Jin Mu: She was so young and yet she managed to find the ice stone. I must admit that her divine powers were truly astonishing.
Queen/Shaman: I heard Jin HoGyeong is unaware of her daughter’s death and is still looking for her.
Jin Mu: That is why I plan to find her. I will find the daughter that she so longs to find, and make Jin HoGyeong become my puppet.
Queen/Shaman: How are you going to find a dead girl?
Jin Mu: I will find someone. Someone who will make her believe that she must be her daughter, BuYeon.

Thank goodness that the Queen/Shaman and Jin Mu haven’t discovered that the missing Jin daughter is alive and her body is occupied by Naksu’s soul.

Jin Mu thought the child drowned because her body fell overboard.

But my theory here is, she drowned, her soul was returned to her because the lake itself contained the Soul Ejector. Master Seo had thrown the Soul Ejector in it. The lake contained the black powder. So sure, she could have died but the soul returned to her FOR THE SECOND TIME.

(Sorry, I’ve no time to screenshot. But rewatch the scenes in Ep 7 and Ep 11 to see what I mean.)

Also, in Episode 9, we were shown what happened during the night that child BuYeon supposedly died. She was holding the ice stone, and Jin Mu ordered her to hand it over to him. She shook her head and raised the ice stone. The ice stone then activated by sending out a dark trail of smoke to the skies. The boat started to rock.

And then we’re shown the shadow of Jin Mu holding the ice stone FROM THE PERSPECTIVE of Buyeon bobbing in the dark waters. By activating the ice stone and falling into the dark waters with the dark powder, she had in effect began the alchemy of souls on herself.

And to me, this is when she’d become a Great Soul. She was able to harness the power of the ice stone itself. Unlike the other soul shifters who did AoS with the small glass balls with portions of the Soul Extractor, she UNWITTINGLY performed the AoS with the actual ice stone, in the lake full of Soul Extractor.

Unfortunately/Fortunately, Buyeon doesn’t remember all this when she came to. The easiest explanation is that she had amnesia after she came to on dry land.

6. BuYeon is the ice stone.

Having performed AoS with the actual ice stone, BuYeon/MuDeok was recognized by the relics in Jinyowon in Episode 5.

It’s noteworthy that when Naksu was sucked into the mirror or when she was banging on the glass, the relics ignored her soul and her body, that is MuDeok’s body.

But once the Great Soul (or blue energy) emanated from her while “touching hands” with Uk on the Mirror of Longing, the relics in the Jinyowon became excited. They finally recognized the ice stone inside of MuDeok’s body.

They said, “She’s here!” “It’s her, the blind girl!” “It’s the ice stone!”

So yes, if I take the relics’ words, literally and symbolically, then BuYeon is the ice stone. She is the ice stone, incarnate. Incarnate meaning if the stone became flesh and bones, then it would be BuYeon. (Just like for Christians, God made flesh is Jesus Christ.)

Anyway, these are MY THEORIES. As you can see, I cited the dialogues on which I based my theories. It’s up to you to take them or leave them.