Realms of Eas

Spell circles could be formed from mana, but for bigger and more complex applications she had always engraved it in metal. Stone and earth seem to work to some extent as Sarah had tested a couple of hours ago. So what prevented her from doing the same with water she created?
Acting on the thought, she created her usual sphere of water, before forming it into a torus and flattening it, then she slowly started to let it flow into the shape of a simple spell circle. In her old world she would have used a light spell, but her water sphere spell had become a better choice due to her affinity.

[Your Water affinity has reached Lv 13.]

However not even halfway there she noticed the first issues: with water being a liquid, she needed to employ additional spells to force it keep the form. In addition, the spells she used started to become unstable, if she didn't concentrate enough.
The flow of mana of each one was most likely interfering with each other. Something which wasn't an issue when one used a few minor spells to form an arrow or water jet, but it looked quite different on a complex shape, which in itself should aid in casting magic and needed multiple assisting spells to keep its form.
Dispelling her experiment the mage concluded that anything but solids and mana wasn't practicable to be used as spell circles.

But...
What about souls? While they looked to her like something fuzzy and hard to grasp, her soul sense was still level 1. Maybe they could be used... Though in the end that would create a chicken-egg-problem. She needed control over souls to gain control of souls. And at that point she could just use the souls to control spell circles generating mana to sustain them-self, if her theory was correct.

She should have chosen earth, as she had the chance. But lamenting her decision now wouldn't help her. She needed some way to carry her bigger spells and preferably something, which wouldn't disintegrate on the first use like the ground before. Ice could also work... Maybe she could freeze her water? Unfortunately it wasn't part of her affinity and holding unoptimized spells just with mana wasn't easy, so Sarah quickly requested a bunch of arrows from her sister.
It would have been better, if she could have gotten a few more swords, daggers or metal armor. Unfortunately Sera didn't want to part with yet another sword as a sacrifice for the progress.
Arrowheads it was.

A few fights and some failed experiments later she had a bunch of newly engraved magic items.

[Icy Arrowhead

Quality: average
Effects: Will slowly freeze their surroundings, if provided with mana.
Description:

A common arrowhead enchanted with a temperature reduction spell. Some may say that it is a faulty product, as the effect can not be used once stuck in an enemy, however its creator had other uses in mind.
Their user is advised to handle it with care, as the reduced size of the enchantment makes the item quite fragile.

]

 
Unfortunately Sarah had experienced the last line in the description more than once. Hopefully she could now continue her actual experiment and not only try to make some decent equipment.

Placing the arrow heads on a floating pond of water, they quickly froze it's surface with a bit of mana. While the ice wasn't anything like metal and probably not even as strong as rock, with it being made from water she could repair it much easier.
Getting to work, she started to engrave a simple spell circle as a test.

Walking, keeping an eye on the still very common fights, not that she actually paid attention, and engraving lines into the ice sheet, It was quite a taxing process. If she had worked with the ground, she could have saved concentration and time, but the mage made progress. The fact that she could repair shattered or wrongly engraved sections helped.

Carefully pushing mana into the finished circle a small sphere of water appeared above it.
That she still needed to repair the ice wasn't optimal, but she could work with it.
Fortunately, or maybe unfortunately, the third floor had taken again longer than Nia had expected and Sarah still had seven floors to create her soul trap.

Not waiting to fully regain her mana, her abnormal mana recovery took care of that to some extent, the mage used the conjured water to remove the old spell and restarted her engraving efforts.

 
Getting the spell to a functioning level took some time, but Sarah finally reached that point by the time her teammates were finishing an encounter. Though she wasn't sure how many of them had passed in total while she had been working on her ice. If she hadn't been lost in thought, she probably would have also questioned where all the beasts were coming from, however Sarah had been occupied.
Ignoring the questioning look of the other two girls, she got closer to the dead or dying bodies. ... and noticed that she forgot to add some way to place the body on top of the spell. Well, she could probably let Sera handle the heavy lifting.
Carefully lowering the sheet of ice, Sarah froze it to the floor next to a smaller spider, not that there was actually much of a difference between all of them.
"Sera, can you place that spider on the ice? And please do it carefully."

"I hope whatever you are trying to do doesn't take too long. All those encounters did stall us and we probably won’t make it in time if this continues." Before her sister could act, Nia interrupted them.
Sarah chose to ignore the statement and waited for Sera to finish her job.

With everything set up, the mage let her mana flow into the construct.
Then her spell appeared, after which the beast burst into smoke as its soul was caught in the mana construct.
As those steps weren't anything new, Sarah had confidence that they would work, but whether the soul would be able to sustain itself and the spell was a different question.

Mana was slowly gathered by the soul, pumped into the spell which returned a part back to the soul and the cycle continued. With the accumulating mana Sarah reduced her own participation, though she still kept an eye on her creation. She knew enough about nuclear power to be aware that self sustaining systems, which grew more powerful over time, could have devastating effects.
However, aside from the still accumulating mana, the soul seemed stable.

Still keeping an eye on the trapped soul as well as holding her connection to the spell, which fortunately only required a neglectable amount of her brain power and gave her mana instead of taking it, she continued the procedure with the other bodies. This time she tried to add them to the same spell. While it would work with one spell for each soul, it wasn't economical and the minuscule amount of concentration would add up.

[Your Searcher of ##### class has reached Lv 21.]

Trapping the two souls of the other spiders turned out fine. The size of one seemed to have some effect on the amount of mana gathered, though there also was only so much one could gather from one point in the first place. It made predictions about the mana generation when adding or removing souls harder, but that wasn't something she couldn't solve with spells meant as controllers.
Those controllers also helped as she started to add further soul traps to the mana construct. Putting all souls in one trap seemed possible, but she had no idea what would happen once they reached a critical density. While she needed to answer that question sooner or later, executing experiments with higher risks without time, backups and fall-backs seemed like a bad idea to her.
Obviously creating such a spell construct was normally a very bad idea as it would need a lot of mana and concentration, aside from the interference of the different spells. However, thanks to her hacking, she didn't need to keep control of the traps herself and mana was irrelevant for this specific case. The inference was then solved by the souls controlling the mana.

Happy with the success so far, before she could continue, Sarah was interrupted by her sister, who apparently couldn't contain her curiosity.
"Hey sis, what are you-" However Sera got also disrupted, this time by the system.

[Quest

Description:

You have shown an unnatural ability in the usage of elements outside of your affinity. While the application is still crude, for the time span since your arrival in the realms your achievements are still far outside the norm.
As such an opportunity has arisen.

Objectives:

- Subjugate the boss on the last floor of the dungeon Foggy Grotto without help and without using your affinity within the next 8 hours (7:63:63 remaining).

Rewards:

- Variable (depending on performance and elements used)

Failure Penalties:

- None

]

 
"-doing?"
Not that she seemed to see the quest window. Though Sarah wasn't surprised by the fact. According to Nia, quests were usually given out in settlements. The only exception being personal quests given by other people or world changing events like the appearance of new realms. Without anyone around and with the personal description this seemed to be some rare case in between the two exceptions.

The scientist would have liked to continue her work on the spell. But how things stood, she could either try to bind the spell to herself in a way which would protect her soul, attempt to compress it in a similar way to how spatial bags worked to hide it, both of which had their own issues and dangers, or go for the time limited reward of the weird quest. With how timely it appeared, the chances weren't zero that whatever she got out of it would help her, especially so, if she used the trapped souls to finish off the boss.

"How long do we still have, if we want to make it in time to the settlement?" Sarah ignored her sister's question for the moment.
"Finally noticing that we are getting through the dungeon way too slowly? About 8 hours, a bit more, for the remaining 6 floors," answered Nia.

The quest seemed maybe even a bit to perfect for their current situation. But preferring the quest over attempting to stuff souls into herself, Sarah still chose it as a less risky alternative.