“Again, why can’t you generate mana?” Felicia asked mumbling.

“Mana needs warmth and flesh and life. It needs emotion and empathy. It needs the warm joy of living.” The voice emanating from the stone lying in the crook of her neck was a lot more eloquent as he recited something akin to a verse. Instead of his previously halted and immature speech, Agren now spoke fluently and with a greatly expanded vocabulary. Felicia shivered in revulsion as she realised where the stone had gotten this competency from. Deciding not to overthink it at the moment, she nestled deeper into her blankets and curled up some more.

“Do plants produce mana?”

“Yes.”

“And you can store mana inside, using it to grow?”

“Yes. I will need another twenty humans to advance.”

Felicia barely managed to stick her head out of the covers before vomiting again. The sour acid she managed to produce stung in her nose and reduced her to a tear-streaked, snotty wreck. She felt the faint tingle dance across her features as Agren took the filth right from her skin. Just like he did to those men.

It was midday by the time she had stopped vomiting. The light shining through the glass cylinder was finally bright enough to force her out of bed. Stumbling out of the dark room, she made up her mind. Breathing in the fresh air that can only be found in the vicinity of trees, she started the first step of her plan. “Make a turtle,” she commanded the stone. The animal in question appeared nearly instantaneously, the barest flash of pink innards telling her that the beast was generated piece by piece instead of it being teleported from somewhere. Studying the animal, she prodded it with a finger. It reacted lazily, poking its head from its shell slowly. “Does this create mana?”

“No. It’s mine.”

“Can you let it go?”

“What? It’s mine. I can make it and take it back. It only costs a bit of mana. I get most of it back.”

“Yes, but can you let go of it? That way, it could start producing mana, right?”

In fascination, she watched the fanciful turtle lose colour slowly. Its shell had been a vibrant mother of pearl look-a-like, and it was slowly turning a dull brown. “That was not fun. I feel sick,” was Agren's muted comment.

“Make sure to bring a doctors note. No pay for undeclared absentee-ism.”

“What?”

Felicia ignored the question. She was about to ask Agren whether the turtle was making mana or not when she sensed it. The animal now had some quality that she couldn’t describe. Where it felt as normal as her own hair before - a part of herself and the world that she received no feeling of touch from - she started feeling the being. The small turtle started glowing in a sense still alien and foreign to her.

“It’s making mana… WHAT?”

“Good. This way we have at least one viable path to advance. Now, Agren, we do some more market testing.” She somehow felt the stone shiver in horror where it lay against her skin.

By the time the sky high above turned orange and pink in the evening sun, Agren was empty of mana. The forest was trimmed back even further, and Felicia was looking at a large number of stone cages. She grasped a freshly re-materialised pen in her hand while looking at the large amount of information she had been writing down. Agren had been getting better and better at fulfilling her weird materialisation requests, and slightly changing the base properties of a uniform material was no longer a stark impossibility. The large sheet of paper laying on the solid stone table was the latest proof of the diamond’s increasing competency.

“I still don’t get any of this.”

“That’s okay. You're dumb as a brick, after all.” Looking down at the efforts of her labour in the fading light, she smiled to herself. Along with all the animals she had the stone materialise inside the cages, she had him recreate her smartphone. She thanked all that was holy for the testing she did earlier. Dematerialising the phone and rematerializing it didn’t seem to cost the stone a lot of mana. It was the ‘adding the bits and stuff that changed, you know. How they are now the same but different, sort off’ that took a lot of energy. Felicia had accosted these difficulties to changing data on the storage media in combination with the changing battery charge. Also, her phone had little charge left when Agren had stolen it from her, so she needed a new battery after every half hour of smartphone use. The amount of mana lost in absorbing an empty battery and materialising a new one was relatively small, so she had been able to coalesce all of her findings in one of the pre-installed spreadsheet apps.

Felicia decided to try to enlighten the stone once again. “The biggest being you can materialise is that turtle, right? The smaller beings are unknown to me, because I can't see them.”

“The smallest one is great! It takes these long thingies and turns them into this floating thingy and this shorter thingy.”

Felicia suspected that the stone was telling her about some bacterial decomposition process in its own dumb way. She again firmly decided not to give any attention to the concept of a stone messing with stuff on the microbiology scale. Instead, she continued recapping her findings. “The turtle is slow. Not only in movement, but also in the way it generates mana. Those small thingies you can make are too fast. Bacterial decomposition needs a steady supply of fuel. Finetuning this process could be extremely beneficial, but we have found that this process requires too much precision to be viable.”

“We did? I didn't know that.”

“Just shut up for now, okay? You know what, let’s just skip to the conclusion. I want you to make as many mice as possible. Be sure to let them go, to release them from your control. Also, make a lot of plants that they can eat. The plants can remain in your control.”

Felicia watched with muted fascination as a mouse flashed into being in front of her. She was surrounded by a large array of stone cages and boxes. The square constructions made a neat array of sizes. The biggest one contained the aforementioned turtle, the smallest ones became too small to see. They had spent the entire day in experimentation, trying to find the optimal mana generator. Turtles were too big, while insects were too small. She had concluded that there was a lot of interplay between metabolic rate and mana. Finding the best ratio between mana needed to stay alive, mana generated and heartbeat had taken her many hours. Angren had been stubborn in following orders in his own way and had even refused to follow some of them. The feeling of releasing his own creation had felt - in his own words - like lovingly making a treasure before letting someone else destroy it in the worst way possible. She had been unsympathetic to the stone’s complains and forced him to follow her orders. The nature of their bond was still a mystery to Felicia, but she suspected that she had been extremely lucky in getting the core to divulge its true name to her. Not telling him her own full name had been another extremely lucky break, she suspected.

In conclusion, the animal that will support the best growth trajectory is the humble little mouse. Insects seem to lack the biomatter needed to sustain a sufficiently large enough amount of mana. Larger mammals - like the colourfull turtles, oddly horned bunny variants and other critters - contain more mana, but their increased physical and magical mass introduce too much inertia. Mice had turned out to be the perfect combination between size and lifespan. “You can absorb all the cages and animals now.”

“I can’t.”

“Yeah, you can.”

“No, they need to be dead first.”

Felicia stopped happily strolling around. She had managed to forget the unexpectedly large impact that the feeling of helplessness at nearly being raped had caused her. Sighing a shuddering breath of air, she grabbed a large branch. “Right. Let’s get to it then.” The feeling of smashing all the small animals the moment they regained their freedom did a great job of distracting her from the scarring events of the past few days. Agren removed the stone cages one by one as Felicia brought the club down on their innocent little heads. Except for the small mouse. That one was freed, along with all the insects small enough to become mouse food. All the mana Agren regained from absorbing the mangled corpses went into more mice or food for mice. By the end of the day, the previously barren clearing was filled with dense bushes and ground-covering plants, a myriad of nearly identical mice scurrying along them.

“By the way, did you make males and females?”

“Ow…”

“Right.”