Although Dream's soul opened up an area for the skill, the shell wasn't the only place that the Hierarchy skill would occupy.
Dream knew how complex the skill was. He could tell by how long it took Sophia to modify it. She's never had so much difficulty before with any other skills. But now that she had totally modified it, it was time to actually give Dream the skill. And knowing how extensive it was, the skill would have to not only occupy space in the shell, but the space in between the shell and the nucleus. With this, there would be 3 layers to Dream's soul.
When Sophia got her hands on the data for a skill, she could do three things with it. She could either write a new skill to Dream's soul, hold the data for the skill and do nothing or mess with it, or integrate the skill with another existing skill. Unless she did either the first or third option, Dream wouldn't gain much from the skill data.
For the most part, whatever skills Dream got would be thrown into one of his three main skills. Those skills were very broad in their application so they could accept all kinds of skills easily. It would only serve to strengthen or optimize the skill. But for some skills, they were too complex or unique to integrate. This was the case with Hierarchy, and Sophia needed to write an entire skill just for it.
While they didn't know how it worked, working with the data of a skill wasn't difficult. Only writing it took some energy. Usually it wasn't a large amount of energy since most skill edits were small. But in this case, the energy expenditure was going to turn out to be large.
Not only that, but the Hierarchy skill Sophia was very different from the original. Not just because she had modified it, but because she would also be integrating certain aspects of Demonic Regeneration and Mana-Body Manipulation. All three skills worked together, so Sophia decided to create one harmonious skill out of them.
As soon as Sophia started producing the string, Dream could feel energy being sapped away from his soul. He was surprised, but didn't let it bother him as he just let Sophia do her thing.
The string quickly got longer and longer as it piled around the void in his shell. Said void was quickly filled, and once it was, Sophia sent the string into the gap between the shell and nucleus to fill that space.
This process didn't require anything of Dream, just his energy. So he just laid with Luna and Iris as the string kept on piling around. He was glad to be comfortable too because the process would take around 2 hours.
After those two hours though, he needed to become active.
By the time Sophia spit out the last of the string, his soul looked like a 3 layered mess of steel wool. Only Sophia could keep track of data in that mess, and using that power, she was able to easily lock onto the ends of the strings connected to the Hierarchy skill.
[Alright. The 3 in 1 skill has been created. Now comes attaching it to your soul. For this, we'll split the string ends into thirds and connect a group to me, your nucleus, and then split the last group in half to connect to the Arcana and Particle Manipulation skills.]
'...And that'll require me to cut enough strings to connect them to?'
[Unforutnately yes. I'll help you and try to dampen the pain. Though you should mentally prepare yourself, because there's several hundred.]
'*groan* Alright. Let's get this over with.'
Dream preemptively grunted in pain as he resigned himself. He also went and grabbed Luna's hand.
"Hm?"
"I'll need this for a bit."
Luna tilted her head as their fingers intertwined. She didn't know what was going on, but she didn't question it as she started stroking his hair again, giving him whatever comfort he was looking for.
'Alright, let's start.'
Steeling himself, Dream and Sophia moved their influences over to his soul. The first place they were going to cut at were the Arcana and Particle Manipulation skills. The reason they didn't choose the nucleus first was because that would weaken his influence, so they wanted to save that for last.
[132 cuts total for both skills. Follow my lead.]
'Mm.'
Nodding, Dream followed Sophia to one of the strings in the middle of the Arcana skill. After arriving, they both encompassed the skill. Sophia then started stimulating the string a bit, causing Dream to feel a burning sensation. Not long after that, he cut the string.
'*grunt*'
Dream winced a bit, but he was pleasantly surprised. The burning sensation actually dampened the sudden shock of cutting a string.
'What's that burning feeling?'
[A kind of concentrated data overload. It weakens that section of the string, making it easier to cut and reducing the shock. While there's no way to make it painless, this should help spread the pain out.]
'Mm. Thanks. Let's keep going then.'
Excited about not having to hurt as much, Dream moved on to the next string, doing the same thing. Sophia also connected the two ends per cut, causing a slight nourishing feeling to course through him.
Like that, Dream went from string to string and cut as Sophia connected. After he started acclimating to the pain, he sped up cuts, doing two or three at once.
It wasn't long before they completed the 132 cuts and 264 connections in the Arcana skill. And after taking a couple of minutes to rest, they moved on to the Particle Manipulation skill, doing the same thing. By this point though, Luna and Iris had noticed the change.
As they could see the state of souls, it gave them more information than just emotional states. It also let them see the energy states and strength of the soul.
When Dream cut the first string, the changes weren't noticeable. But as he cut more, the girls could pick up on flickers of energy. It was very odd, but it told them enough. They knew Dream was directly working with his soul.
What made it even more obvious was Dream's hand. Over time his grip tightened and Luna had to actually activate her mana and exert a good amount of strength to keep her hand from being crushed. This caused her to sigh more than anything. Dream's natural bodily strength without any mana was enough to force her to activate hers.
Unfortunately, this was only the beginning. After the Arcana skill came the Particle Manipulation skill, which after 20 minutes of cutting, was completed as well.
Next was Sophia. Unfortunately for this, she couldn't help dampen the pain by stimulating the strings. What she could do though was take a large brunt of it. Since they were cutting her own strings, she would be able to absorb most of the pain.
Because of this, they only took half an hour to cut her strings and connect the ends. Turns out, Sophia could simply turn off pain for herself. Although she still felt incredibly uncomfortable having her very essence harmed, it wasn't nearly as bad as what Dream had to deal with. Because of this, Dream wasn't opposed in the slightest to letting her take some of the load off him.
The easy cuts only lasted for a bit though. Once they were done with the almost 270 cuts, they had to move on to the nucleus. This is what Dream was most afraid of.
'...Do I really have to?'
As Dream was overlooking all the cut locations on his nucleus with a frown, he asked Sophia.
[Yes. The Hierarchy skill needs to be connected to you directly. The 348 strings that we're going to connect to your nucleus are all the authority bits. Without these, souls that connect to you won't maintain a proper connection. Any souls that you brand also won't be able to be controlled by you. Believe me, you need them.]
'...Fine. Let's take it slow though. If I rush through this, I'm gonna be traumatized again.'
[Of course. Alright, first one.]
'*sigh* One, two, three... Ahhh!!'
As soon as Dream went to clip it, he felt a stabbing pain run through him, his whole body clenched, and Luna and Iris could see the large flicker in his soul.
Sophia quickly connected the two ends to the cut strings, easing a bit of the shooting pain.
"Dream? You okay?"
Luna spoke as he trembled a bit. He just shook his head.
"N-no. Can't say that I am. This shit hurts."
"What are you doing?"
"Just giving myself a new skill."
"Oh... Well be careful. Do you need healing?"
"That sounds fantastic, but no, not yet."
Saying that, Dream closed his eyes again.
He continued cutting and connecting strings, and every time there would be a visible flicker in his aura. It would fluctuate unstably from strong to weak as if it couldn't decide which it was.
This went on for a several hours where he would cut a string every minute or so. This gave him ample rest in between the bouts of horrendous pain.
.........
"Ahh!! Two more!"
Dream let out a yell on the 4th hour. This wasn't the first yell, and the girls had been holding him as if he were giving birth for a while now. They had long since learned what he was doing, and while it scared them at first, they understood he had already gone through with it. He could only go all the way now.
"You got this Dream!"
"Just get it over with and I'll be able to heal you."
"Ahh! ONE! MORE! CUT!"
"Just do it!"
"Make your dreams come true!"
"Haahhh!! Done!"
"Heal!"
After making the last cut and connections, Dream gave the word. Smiling brightly, Luna quickly activated her skill, revitalizing and stabilizing his soul. Iris also sent in nourishing energy.
"Hahh...Hahh..."
"You did good." (Luna)
"I... I hate doing that."
"As if you do it all the time." (Iris)
Iris snickered as she laid on his heaving chest. Dream just calmed his breathing and checked out the notification that popped up in his vision.
<You have attained the Passive Skill: [Nexus]>
'...Nexus?'
[We combined all three skills and heavily modified them. I'm not surprised the skill classification changed.]
'True.'
"How are you doing?"
After looking at the skill and recovering for a while, Luna spoke up worriedly.
"I'm all right. Thank you."
"Good. And you're welcome. You know, you need to be a little less... reckless about these things. I know you have things under decent control, but your own soul isn't something you should be easily messing with. What if you mess up and harm yourself permanently?"
"I won't. If I wasn't confident, I wouldn't do it. I don't do many risky things."
"Liar. What about you sneaking into the United Empire and stealing their treasure? Or you almost blowing yourself up with a nuclear explosion while playing with magic?"
"...You heard about that?"
"Uh-huh. We also saw the aurora lights in the sky for the several days it lasted."
"...That's one of the few mess-ups I've ever had. And me sneaking into the Empire wasn't that dangerous. They don't have a clue who took the heart."
"It was still risky. I'm just saying that you need to take more care of yourself. You worry me sometimes..."
"...Sorry."
"*sigh* It's alright. I guess supporting you and Iris really is my job. A bit of anxiety and worry is natural when I think about it."
"...I'm glad that you're by my side. Both of you."
Dream reached out and put his hand on the side of Luna's face, to which she nudged into. He also stroked Iris's warm and silky fur which she always enjoyed.
"...Alright. Now since I have this skill, time to use it."
"Mm. What skill is it anyway?"
"It's called Nexus, but it was originally the three skills that the demons have."
"Those Hierarchy ones?"
"Yes. I combined and modified them. And I'm planning to use it on Aegis."
"...Interesting."
"Very. Now, are you ready Aegis?"
"Of course, my lord."
Speaking from within, Aegis acknowledged Dream.
"Great. Then let's activate it."
"Shouldn't you rest first?" (Luna)
"It'll be fine. It won't take too much energy to accept a willing subordinate."
Saying that, Dream activated his influence and mana. He didn't spread it out though. Aegis was next to his soul, so all he had to do was target the space right next to him.
'Alright, I've got the gist of this skill. Brand the soul, form a connection. Since he's a subordinate, his essence will open itself up to me. I'll have full access to his power and skills, and I'll also be able to give him some power.'
[That's the gist, yea. I've already prepared everything.]
'Then go ahead.'
[Activating [Nexus]...]
After she spoke, a line of influence latched onto the pseudo-soul that was Aegis. The soul existed as part of the heart itself, so branding the soul was the same as branding the heart. And although they didn't understand what the material the heart was made of, it didn't prevent them from interacting with it. This was especially so when they had the assistance of Aegis who wielded the Will of the heart.
After activating the skill, Sophia sent its power over to Aegis who shut down any form of defense he had. The heart was laid bare, and the power of the Nexus skill made contact without inhibition.
[Beginning subordination. Aegis, do you accept subordination?]
"I...Accept."
[Good. Creating master-servant contract...]
With that, the power of the skill seeped into Aegis's soul and created a batch of strings that wove into it. These strings made up the contract, and with it, Dream would have full control over Aegis's being.
It didn't take long for the contract to root itself. The two already had somewhat of a connection, so using that as a guide, it was easy to overlap the Nexus skill's own link. And once it was, Dream could sense the entirety of Aegis's power.
[Subordination complete.]
'Very nice...'
[Would you like me to do a one over of his skills? When Aegis combined with the heart, his enchantments were overwritten and turned into skills. They're weak versions though, and should we upgrade them, his control over the heart will magnify.]
'Sure, why not.'
[Beginning upgrade.]
Using the new Nexus link, Sophia sent her influence into the heart where Aegis's soul resided and targetted the skills.
There were many skills, and all of them were weak variations of the enchantments that Dream had given Aegis as a suit. Things like stealth, particle manipulation, thermal control, magic, and so on.
There was a problem with the heart overwriting the skills though. Dream and Sophia had designed Aegis as a kind of symbiotic being. All his abilities mainly worked alongside Dream's, not independently. This served to enhance Dream's own usage by using Aegis as a kind of amplifier.
But even then, the purpose of the amplification was to use Aegis as an armor and weapon. Aegis's stealth wasn't necessarily to enhance Dream's own stealth, but to stealth the armor. Aegis's particle manipulation wasn't entirely to enhance Dream's own skill, but to strengthen Aegis's material strengths. And his magical network wasn't created to enhance Dream's base magical abilities, but to strengthen the magical armor aspect of Aegis as well as his magical mediary capabilities.
Dream used his skills alongside Aegis to power and strengthen what Aegis was. The boosts to his own power weren't large, and perhaps the only real large boost that Aegis gave Dream was an external mana source.
But now with Sophia rewriting his skills, she would be able to use those skills to harness the power of the heart directly and then find a way to use it to strengthen Aegis's functions and channel some power to Dream.
The boost in sheer power wouldn't be astronomical, but the precise applicability would be greatly enhanced. Before, Dream used Aegis and the heart's power crudely. But with this skill rewrite, he would be able to precisely wield both, giving him greater power that came from technical skill rather than sheer power output.