The inside of the wellhead built with bricks in the basement leads downwards through steps and passageways. After walking for a dozen steps or so, the stairs reach their end, and the passageway suddenly opens up, the surroundings resembling a karst cave.
This here is the island's heart tunnel.
The cold, damp smell mixed with a faint acidic hint in the dust fills the nostrils, despite the light from the lantern. Darkness rushes in from all sides, as if it wants to seize all senses.
The path within the mountain body is left with only a steep slope composed of jagged rocks and is not continuous. Sometimes, one must carefully leap over slippery cliffs, below which lies a bottomless abyss.
Some slopes have simple steps hacked out with a sharp tool, supposedly cut by Zoe's father to make walking easier.
The steps are spaced just short enough for someone of Zoe's height to step down. Linking it to the group photo seen previously, Li Ang guesses it was cut to fit her mother specifically.
The young girl's small head surveyed the underground cave-like landscape: "I've never seen scenery like this before."
"This kind is called a karst cave."
Li Ang pointed at the stalactites, stalagmites, and the worn smooth surfaces of the mountain that he illuminated with the adventure lantern: "In general, terrain like this is formed by the long-term influence of underground water on the mountain body."
"Generally speaking? Isn't this the case here?"
"The water bodies of Satus Island don't seem capable of something like this."
Zoe asked further about what 'water bodies' meant, and Li Ang explained it as a general term for various natural water areas in a region.
More than that, he couldn't explain, because the natural ecology of Nebis World is very abstract. Or perhaps it's beyond abstract, as a person from Earth, he can't comprehend it.
This world doesn't have oceans; the sky islands are isolated, yet water isn't scarce. The water cycle seems to function normally, and there are many natural environments similar to Earth.
This is because a large number of elemental spirits participate in the world's ecological cycle.
In the foundational triangle that composes the world, of spirit, magic, and matter, the smallest units composing matter are the elements.
Over 96% of these elements are composed of the four basic elements: earth, fire, water, and air, also known as earth, fire, water, and wind.
Since they form such a large proportion, most of the time when elements are mentioned, it is implicitly referring to the four major elements.
Elemental spirits are nurtured within the elements. Their spirituality attracts magic to converge and grow, nurturing their matter.
Since all four elemental spirits want to increase their faction's total amount but are restrained by each other, a cycle of give and take is formed, and thus the world maintains a stable cycle.
In the cave before us, it is precisely where the water elemental spirit has replaced the natural water body, thus presenting the karst cave landscape.
"I feel there are many earth spirits," Zoe said.
In the darkness of the abyss, gusts of wind ascend, their magic so dense it makes it difficult for Li Ang to maintain a steady breathing rhythm, almost as if the wind is blowing pure magic.
"Yes, these surroundings are all soil and stone, an environment favored by earth elemental spirits, and under their vigorous summoning, magic is very abundant."
"However, this is very unusual."
Li Ang said, "The first time I started mining, I tried to command the earth spirit to summon an earth giant, only to find that the earth spirits on the whole of Satus Island were scarce. I thought it was because the resources here are poor, incapable of nurturing elemental spirits.
"But now, it seems they are all within this abyss.
"Elemental spirits are a part of the world's cycle, they don't simply run towards benefits and away from harm, it must be something binding them here."
"Star Soul," Zoe immediately said.
"Correct."
Having said that, Zoe's expression became much more serious.
The underground passage isn't very long, because Satus Island isn't very large, its vertical depth doesn't exceed its horizontal width, the two can cross the island in a day. So after about an hour or two, the scenery below began to change rapidly.
First, there appeared light.
Fluorescent stones began appearing within the mountain walls, each the size of a goose egg, containing faint magic power, emitting light predominantly in shades of blue-green, with a bit of pale yellow and pink.
The fluorescent stones became more and more numerous, until they lit up the cave passage as bright as daytime, reflecting colorful glimmers in Zoe's cat-like, wide eyes.
Each time she saw a cluster of fluorescent stones, she'd almost always go over to pick and choose, then compare the smooth ones she held, eventually selecting one with difficulty, and carefully placing another back where it was.
Reaching this stretch, the terrain was flat and continuous, allowing Li Ang to divert his attention to reading his journal. He wanted to see if there was more information on the Star Soul, finding a way to deal with it would be ideal.
"Year 293, February 9th
"Cha'ain was severely injured, but he obtained information about the Star Soul at that ruin, we agreed to discuss it in detail in the coming days.
"Zoe started learning swordsmanship, she is very healthy, which is wonderful.
"But Lily...
"She never talked much about the Esoteric Buddhism, but she gazed at the sky more and more, then fell into a state of heightened perception, saying she was seeking divine revelation.
"Does this world truly have gods? Perhaps. I should maintain a reverent heart. Every time I see Lily in that state, even though I've been in the Legendary Realm for a long time, I can't help but feel a shiver."
Another piece filled with information.
The path ahead was blocked, a cliff appeared in front of them. Reciting the contents to Zoe, who was browsing the subterranean scenery beside him, Li Ang put away the notebook.
Unlike the earlier sections of the island core path, the world here was increasingly bright, more like another world than the underground.
"Wow, it's beautiful," Zoe exclaimed.
Besides the commonly seen minerals in Nebis World, which are more common in the island core, there was a substance similar to gold appearing among the Fluorescent Stone.
They covered various rocks like plating, and after reflecting the fluorescence, the entire space was as bright as daylight, allowing Li Ang and Zoe to see the things below the cliff.
The cliff was not high, about a dozen meters, below were creatures similar to lizard-like Demons chewing on minerals.
Upon hearing the footsteps of the two, they took fright and quickly burrowed into nearby ground holes.
"Truly wondrous," Zoe remarked after staring below for a long time.
Li Ang had not entered the island core path many times, and each time had its own scenery.
The island center was a place where one could distinctly feel the Otherworld sensation. The essence of the Earth, the secrets of the world, the sighs of mortals converged here, jointly heralding — ahead was no longer the mundane world.
As they were about to leap over the cliff, Zoe suddenly screamed and hid behind Li Ang, not daring to peek out.
"What's wrong?"
"T-there's a ghost over there!"
Li Ang probed in the direction she indicated, spotting a human skeleton.
The bones were not intact, bearing signs of Demon gnawing. He surveyed the surroundings, roughly deducing the route the person had fled, and the place they came from was already blocked.
The blockage was man-made, caused by landslide from Magic and Weapon attacks.
"This should be a resident missing from Satus Island," Li Ang guessed. "Years ago, the split island core path wasn't the only one, some villagers mistakenly entered deep into the island core. After your parents came, they completely sealed off the other paths to prevent further entry."
"But they couldn't explain to the villagers where the missing people went, leading to misunderstandings."
After Zoe remained silent for a moment, she suggested burying it, and only after they finished did they resume their journey.
After leaping over the cliff, the road ahead was not as narrow as expected in the subterranean world, but rather more expansive.
Layers of gold-like cover increased, countless beautiful minerals like Turquoise, colored crystals, quartz, and chalcedony lay among them.
The pretty stones uplifted Zoe's mood, she was busy picking them up, but despite picking some and leaving some, she still desired so many that her arms could not hold them all, and there were still better-looking ones ahead.
Ultimately, she let them all go like a deflated balloon, eagerly darting forward. The metal sound of the armor built yesterday echoed in the passage.
Suddenly, the road ahead was blocked by some collapsed rocks. They searched for a new path among nearby rock walls and crevices.
They discovered a narrow passageway, cramped and rugged on the surface, but after a short distance, it became a tunnel illuminated by gems.
The tunnel walls were so orderly as if built by humans, walking here meant nothing to worry about. Li Ang flipped open a new page of the notebook.
"February 25, Year 293
"Talked with Cha'ain for a long time, we probably have some understanding of Zoe's situation. She and the Star Soul can be seen as mutually needed, she can gain the other's Power, and so can the Star Soul. But if the young her rashly contacts it, she'll only become its nourishment.
"She needs to grow, but that doesn't mean we can just watch her grow up. Because after gaining the Power of the Star Soul, what it means for this world, for the organization, we don't know.
"So Lily and I decided, we must go fight against the organization.
"Though we can't accompany Zoe as she grows, we both feel regret, yet more so we want her to live in a carefree future.
"We didn't feel hesitant; for her, we want to uncover the truth of the world.
"This will be a difficult journey, possibly until the end of the clouds, the ultimate end of the world."
Reading the notebook, closing the paper pages, Zoe pointed excitedly upward and exclaimed, "Look!"
Before them, the sight suddenly filled Li Ang's vision.
He could confirm, they also saw the ultimate end in a certain sense.