...It can be observed that large amounts of evolved animals, now often referred to as 'monsters', gather in places with high mana concentration. These places are usually notable for their abundant and sometimes even excessive amounts of vegetation. While the correlation between lush growth and mana was initially unknown, it was later confirmed by mind-evolved humans, which are sensitive to mana. Such places are hereby referred to as 'monster nests', usually having further evolved and quickly multiplying monsters. As such, monster nests are a priority target for elimination...
-An excerpt from 'Mana and Evolution' by Joseph Larring, 25 AA
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Once the herd moved in, Lan began filling the newly made cave with neutral mana. Once again confirming Lan's theories, the concentration of it was higher than it was outside.
Under the influence of the mana increase, soon various kinds of moss and mushrooms began quickly propagating along the walls and the floor of the chamber. Such mana-infused plants would surely be good food for the herd.
Having done that, Lan continued digging a tunnel leading further down, making an exit from the chamber opposite the entrance. He dug it in the shape of a large downward spiral, which went alongside the expanding edges of the domain, to maximize the use of his domain in both width and depth.
Such a large undertaking once again drained his mental mana, forcing him to turn his attention to other things.
First of all, residual mental mana from his linked creatures which died one way or another.
While it didn't get absorbed immediately, instead floating around the Core, it didn't stay that way forever. It was slowly being absorbed, like water flowing down a clogged sink. As such, the residual mental mana, or the 'soul' of the deceased Greater Deer was almost completely absorbed by now, with only a tiny amount of it remaining.
Lan guessed it had something to do with his earlier mana infusion and the linking process, but he wondered what he could actually do with it.
First, he looked at the 'soul' of a recently deceased mouse, which was killed during a collapse caused by the construction of the hill by Lan. Oops.
It was still largely intact, so he pulled it away from the Core and then began to think of uses for it.
'I mean... If I treat this as a soul, then maybe resurrection would be possible. Wouldn't it be a perpetual engine if things died, I resurrected them and they fought again? My growth would be endless!'
Inspired by such thoughts, Lan found the corpse of said mouse, and by manipulating earth mana, pulled it towards the surface.
Once again pulling its' soul, bringing it back to the body, he 'pushed' it back in. The soul was absorbed back without a problem.
Then, the body jerked and shivered, the reborn mouse opening its eyes again... Only to start squealing in pain, unable to move.
'Riight... While it died from suffocation, its' bones were broken during the collapse, and resurrection doesn't automatically heal its' wounds. Oh well, nothing a little magic can't solve!'
Once again proving its' usefulness, mana-infusion quickly repaired the broken bones, with them snapping back into place, the mouse even gaining in size in the process.
Soon, instead of a lifeless and broken corpse, now an incredulous mouse was sniffing around, not really knowing what just happened. While to Lan, this once again expanded his skillset.
'Nice! That means I can respawn stuff! Perpetual mana engine, I am coming for you!'
Filled with excitement, Lan quickly found another corpse, one left behind by a little bird which fell out of its' nest and broke its' neck. Quickly identifying the soul belonging to it, which was still intact, Lan tried putting it back in as well.
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However, this time he was not met with success. After the corpse jerked, it lay still again, the soul floating back out without even giving Lan the time to heal it. The soul once again rushed back to the core, now even smaller than before, soon being absorbed, never to be resurrected again.
'...That didn't go so well.'
While unsuccessful, this gave more information to Lan.
'Okay, so the body must be in a state which can support life for some time. If it can't, such as having a crushed head, being decapitated, or destroyed beyond healing, then respawning is impossible.'
The excitement of initial discovery having died down, now knowing the drawbacks, the idea of respawning didn't seem so viable anymore.
'Now that isn't useful at all! I mean, after a fight the body is almost always eaten, who even leaves it intact? And then even if I try to resurrect an animal after a fight, it would probably get 'spawn-killed' again, only wasting the mana and the soul... Ugh, mana alone can't solve everything.'
Indeed, while mana is a form of life-bringing energy, energy can't completely replace matter. And without having a way to create new intact bodies, resurrection would be largely useless. Still, Lan was able to resurrect the animals who died in smaller accidents, so there's that.
Still, during the time Lan spent experimenting with souls, his mental mana fully recovered, allowing him to continue digging.
After finishing a segment of the tunnel which was around 50 meters long, and moved downwards, still being tall and wide enough for even a Ligtning Horn to pass through, Lan once again began digging a chamber, a bigger one this time, at around 40 meters underground, giving Lan more space to work with, without worrying about the ceiling collapsing.
He once again expanded outwards, compressing the ground and stone together, fusing into the sturdy walls and ceiling.
The end product was fifteen meters tall, and a hundred and fifty meters in width and length.
Then Lan began cycling mana through the new room, filling it with magical energy. The result was different from what he imagined though.
Even though this chamber was deeper underground, it logically should have had a bigger concentration of mana than the entrance chamber. However, it was instead lower, puzzling Lan. After comparing the two though, he found where the problem lay.
'...Aha, I got it. Though the upper chamber is closer to the surface, it is smaller, thus mana is more concentrated, the second chamber however is much bigger, and the advantage of being deeper is nullified by being larger.'
Having identified the problem, the Core quickly went to fix it. And the fix was simple really: lowering the size of the room.
So, Lan reduced the size from one hundred and fifty meters to one hundred, still leaving plenty of space for the future dwellers, and increasing the concentration of mana.
From this whole ordeal, he gained valuable information for future digging: The size of the chambers may increase only as one gradually goes lower because otherwise, the concentration of mana will be unsatisfactory.
As he was finishing up the new chamber, it got an unexpected visitor, the Lightning Horn.
Even without a command, it moved downwards towards the new chamber, the herd following closely behind it.
Lan was confused. While deer are able to live in caves, they aren't really underground dwellers, as their food is usually on the surface, so why would they move here out of their own initiative?
As he was pondering though, new vegetation sprouted up along with the increase in mana, and the herd was already nibbling on it, absorbing mana within. Through this, answer immediately became apparent.
'...Is it mana? Is the fact that mana-dense areas have food with more mana make animals instinctively seek them out? And because of this, when the herd felt higher amounts of mana flowing from the tunnel, they instinctively went down? Guess that's the ecology of a magic world for you.'
Though the deer had a stable source of food and mana, Lan noticed that they still lacked water. It was probably thanks to mana that they weren't dying of thirst by now.
As such, Lan went looking for water within his domain. It didn't take him long to find a small underground stream flowing not far from the surface.
Lan then started carving a channel not far from it, leading into the second underground chamber, then coming out of a wall. In the chamber he carved a shallow channel on the floor, mimicking how a stream on the surface would look like. That channel was carved across the room, dissapearing into the wall opposite of it. Lan carved the channel connecting it back to the stream, forming a loop. After that, he carved into the stream itself, and water, having found a new path, quickly flowing through.
'Water supply established! Can't exactly call myself a professional plumber, but hey, it's a start!'
Having more or less finished the second chamber, Lan turned back to the first one, which, unexpectedly, already had new occupants.
The remaining wolf pair, which was hanging around his domain recently, was eyeing the mana-filled cave for a while now. And now that the terrifying horned herd moved downward, the wolves, probably with their sense of smell, quickly found out.
They soon settled in the corner of the chamber, making themselves at home.
When Lan was scanning the wolves though, one detail attracted his attention.
The female wolf was pregnant.