The Final Encounter?

As the lights in the underground grew brighter, like soulless mockeries of old Sol's grace, they signaled a new day's beginning. Uria, getting out of bed in a slightly sluggish manner, gazed outside her window. Seeing the steel and concrete city, she smiled, and with slight bags under her eyes, got ready to set off. As for why she had spent a somewhat sleepless night—it was both due to her excitement and the interdimensional scammer haggling with her regarding her "cheat."

Crashing into a lady's room in the middle of the night, wearing a businessman-like suit, suitcase in hand, he got to the gist of it very quickly. And so began an hour-long negotiation about what powers she would get.

"Oyaaa! Here I am, here I am. It took a bit longer to bind a root to your soul, but congratulations, you can now have a cheat directly tied to your soul, a privilege for only the greatest of reincarnators!"

"I don't want it," she replied.

"I know you're excited to—not want it, what?" Having spoken confidently until just now, amidst his shock, he forgot to maintain his suit and suitcase. The shadow, now just being a colorful ray of light floating in space, quickly reformed himself into the previous business attire, with the exception that he was quiet.

"Why would you even offer a power to me in the first place when there's nothing in it for you is my main concern. There's no free lunch in the world, so what's the caveat?" she asked.

"Well... To an extent, that's true. What if it was free though, because of my personal feelings?" Turning to face her and matching her gaze, the shadow slowly spoke.

"Huh, personal?" With a shocked expression, she continued, "Don't all of your kin originate from the lowest dimension, so that's why you can freely influence any world you want by using your... 'deals'? What ties would you have with this dimension?"

"Yes and no... I don't think you'd want to know too much about how the layers are structured, would you? The basics is that we don't make a deal with the person, but with the dimension itself. As for the reason..." he suddenly went quiet. 

"No, I'd very much like to know how it's structured. I do remember that... If you go 'backward' or 'forward,' you go up or down the timestream. I don't know about 'up' and 'down' though, or 'left' or 'right.' It was something that the old geezers in the academy used to study."

"I'm surprised you know even this much if I'm being honest," the shadow said. "Think about it... like a building. Everything rests upon the foundation, right? The lowest layer upon which everything is built is called the Dreamspace." The shadow made a small house from rays of light. "And yes, while it is forward or backward that changes the state of the house between being built or not, going left or right is a different house," saying so he made a slightly different house next to the first one. "A house that's usually quite similar yet not, it is a different house after all. That's the parallel worlds. The exact same thing yet with slight variables for each one of them, and there's countless of them."

Stopping here for a moment, he corrected himself. "Well, not countless. Usually a few hundred thousand. At most. Most decisions won't create a parallel world. And a lot of the time even if it is created it is destroyed within minutes because the consequences in the grand picture of the world were too small."

"I see, I see. Then what about up or down? How does that work?" Now knowing two perspectives, she asked about the final one with curiosity apparent in her eyes. Not many would get to know such things as easily as being told directly.

The scammer changed the building into a very tall cylindrical tower and started explaining. "When you go up a floor when making a building, the floor obviously relies on the one underneath, right? Well, it's the same with the layers of space. While the lowest layer has barely any rules and the energy is freely manipulated, if you go up a layer there's a few more rules from the layer itself. Those rules combine with the previous one's rules. And the higher you go the more layers' rules are combined. That's why, even if there is almost the same amount of energy between a high-level world and a middle-level world, you wouldn't really be capable of harnessing that energy at all as it's too restricted, making supernatural things and similar an impossibility. While you'd have a barbarian punch a mountain into dust in the middle layers. That's why those underneath can freely influence their current layer to influence a higher one for almost no price. Amd obviously the energy density will be far higher in the lower worlds, since theyre closest to the foundation."

"I understand now, thank you for your explanation. So how did you end up having personal feelings for this world?" she asked.

"Not me... But this is my old disciple's homeworld. He fell down into the lowest layer due to the ripples of a battle affecting this dimension. He used to talk about it a lot... And he kept trying to... ANYWAY! I'll sign a contract that you don't need to pay anything, as long as you try to prevent it from being destroyed. Deal?"

Pondering for a few minutes, she finally nodded to him and said, "I still don't want any help with it however. Mostly because I want to grow stronger on my own. I will help you with saving the world since I already started taking a liking to it. That's a promise."

Thinking for a bit, the shadow replied, "Can you at least take something that'll help you grow or something, not a direct strength upgrade but something to help you grow stronger over time. Theres already a root i can use to put something in place and... Id rather increase your odds of getting through everything that'll come towards you and this world."

Looking outside the window, onto the steel city, she kept quiet for a few minutes before she said in exasperation, "... Fine, fine, i agree but lets decide what it'll be first." 

...And so started a heated debate.

"How about being capable of using your Animancer abilities?" he asked.

"Are you insane old man?! Do you think there's anything stopping me from just running out there and infesting the souls of everything if I had that, WHERES THE FUN IN THAT!?"

"Hey, I'm just guessing! What about... increasing your soul-body connectivity?!"

"Giving me physical strength that could flatten mountains?! Are you really okay?!"

"What about summoning your familiars or undead, they could he—"

"NO! I dont want to just drown everything in a horde of skellies."

"How about..."

"NO!"

...15 minutes later.

"...How about making your Quietus grow in reserve the more you kill? And something simple like after an amount of kills you obtain a new slot for an ability."

"That's... surprisingly okay. The limit on abilities you can use sounds annoying after all." For once, not shouting "no" at him, she replied.

"GREAT, HAVE." Realising that a opportunity had appeared in front of him, he struck like a experienced businessman. Waving his finger at her, a simple greenish interface popped up in front of her. Yet before she could look at the contents of the screen...

"BYE!" As suddenly as he came, the scammer left. Left alone in her room, she looked at the spot where he had been shouting just a second ago, now empty. With slight worry on her face, she looked at the interface. Green like a leaf with floral patterns on its edges, it was pleasing to the eye. There were only two beautifully written lines in elvish cursive on it:

Energy absorption

And

Additional ability slot progress: 0/100

Looking at the text, feeling that something was wrong but not being capable of telling exactly what, she decided she would find out as much as she could during her first mission later today. Going back to sleep, she hoped for the dawn to arrive even one bit sooner.