An Youyu turned around.
Hanging on the left wall of Luotu Firm was a long, narrow map of sea layers, secured at its four corners with fish-bone nails and occupying nearly half the wall.
Most common sea charts in Seven-Masts only depicted the nearby waters. A map like this, which included the entire Salt-Bone Sea and its neighboring sea layers, was something many people in the anchorage might never see in their whole lives.
The map depicted a vertical cross-section of two sea layers.
Each end featured a sea level line, with their deeps oriented toward the center of the chart.
Map of Inverted Sea Layers
At one end, the characters for 【Salt-Bone Sea】 were written neatly upright.
At the other end, the three characters for 【Sky-Lantern Sea】 were completely upside down.
On each side, a set of arrows pointed toward the center of the chart, with the character for 【Down】 marked beside each arrow.
In other words, regardless of which sea one departed from, the center of the chart lay downward.
The two sets of arrows ultimately converged on a narrow grayish-white band.
【Float-Sink Transition Zone】.
The closer one got to this region, the harder it became to tell up from down.
Once inside, a body would neither naturally float upward nor sink downward, yet the pressure of the deep waters remained entirely undiminished.
To cross through, one had to rely on driving their own fish force.
Once past the center line, the direction of floating and sinking would invert.
Someone diving down from the Salt-Bone Sea would begin floating upward toward the surface of the Sky-Lantern Sea, and vice versa.
Deep divers traveling between the two places had long mapped out this route through countless trips back and forth.
The Salt-Bone Sea and the Sky-Lantern Sea were inverted relative to each other, their surfaces facing opposite directions while their deeps joined together, which was why they were known as a pair of 【Twin Sea Layers】.
This structure was not unfamiliar to An Youyu.
Back when he was a water scout in the Zijing Sea, he had seen similar deep-sea maps.
The Zijing Sea likewise had a deep passage leading to other sea layers.
Descending over twenty thousand meters from the surface of the Zijing Sea brought one into the float-sink transition zone.
After passing through the transition zone, one still had to float upward for over thirty thousand meters toward the other sea layer before seeing the sea surface again.
Adding it all together, the distance was about fifty thousand meters, and the transition zone was closer to the Zijing Sea rather than being dead center between the two sea surfaces.
The transition zone between the Salt-Bone Sea and the Sky-Lantern Sea before him happened to fall right in the middle of the two sea surfaces, and it was strikingly close.
Descending three thousand meters from the surface of the Salt-Bone Sea allowed one to pass through the transition zone. Floating upward another three thousand meters led to the surface of the Sky-Lantern Sea—the total distance between the two sea surfaces was no more than six thousand meters.
An Youyu shifted his gaze toward the outer margin of the chart.
There, an extremely fine long line looped around almost the entire perimeter of the map.
Beside the line was labeled 【Sea Surface Route】.
Ordinary merchant vessels could not take the deep-diving shortcut through the center of the map. They could only set sail from the Salt-Bone Sea, navigate along the surfaces of various sea layers, pass through transit anchorage after transit anchorage, and loop around most of the map before finally reaching the Sky-Lantern Sea.
The entire journey was 【160,000 Nautical Miles】.
At the speed of an ordinary long-distance merchant vessel, a one-way trip would take about six years.
Circling along the surface required sailing 160,000 nautical miles and spending six years, whereas cutting directly through the deep sea separated the two seas by merely six thousand meters—yet An Youyu did not consider this shortcut easy to navigate.
Six thousand meters only looked close on the map.
The accumulated three thousand Pressure of the Salt-Bone Sea and the three thousand Pressure of the Sky-Lantern Sea would stack together in a certain stretch of water along this deep-sea passage.
The sea pressure there approached six thousand Pressure. To pass straight through the water, one's own strength needed to be at least 【Six Thousand Pressure】.
At the center of the float-sink transition zone was a dark shadow shaped like a fragment of a continent.
On either side of the dark shadow was an eye.
One faced the Salt-Bone Sea: 【Salt-Bone Land Aperture】.
The other faced the Sky-Lantern Sea: 【Sky-Lantern Land Aperture】.
An Youyu stared at that dark shadow for a moment, then looked back at Shopkeeper Xing behind the counter.
"Is this dark shadow the Bone Lantern Grotto-Heaven?"
Shopkeeper Xing set aside the bag of land soil he had just sealed and looked toward the chart on the wall as well.
"That's right. The Bone Lantern Grotto-Heaven is wedged right between the Salt-Bone Sea and the Sky-Lantern Sea. You can enter from the Salt-Bone Sea side, or from the Sky-Lantern Sea side."
"Those two eyes on the map are the entrances on both sides."
"Regardless of which side you enter from, you ultimately set foot on the exact same land."
"The Salt-Bone Land Aperture belongs to Yancheng Anchorage, while the Sky-Lantern Land Aperture belongs to the factions over in the Sky-Lantern Sea. Each guards one gate, and each controls a harvesting area."
Shopkeeper Xing then recounted some old tales of the two sides vying over the grotto-heaven.
As An Youyu listened, the general idea was not complicated.
Ownership of the medicinal plots and mineral veins in the central area of the grotto-heaven had never been clearly settled. Both sides had fought for years, neither willing to let the other send in an extra person or take away a single additional herb.
Because of this, entry quotas and external sales of Land Medicine were strictly controlled.
If he wanted to enter the cavern from the Salt-Bone Sea side, he first had to obtain a 【Passage Permit】 issued by Yancheng Anchorage.
Entering without a passage permit was considered trespassing; once discovered, one would not only be hunted down, but their name would also be placed on a wanted list.
However, a 【Passage Permit】 only convinced the gatekeepers to let one through; the crushing pressure of the deep sea outside the land aperture still had to be borne by oneself.
The Salt-Bone Land Aperture lay roughly three thousand meters beneath the sea surface. To reach it and pass through the land aperture, he needed at least 【Three Thousand Pressure】 himself.
When An Youyu was an interrogator in the Zijing Sea, he had seen case files where people used Sunken Land Grotto-Heavens to smuggle themselves to another sea layer.
A land aperture separated the sea pressure outside from the inside of a grotto-heaven.
Entering from the Salt-Bone Land Aperture meant only enduring the three thousand Pressure on the Salt-Bone Sea side.
Once inside, one traveled by land, and when exiting through the Sky-Lantern Land Aperture, one only endured the three thousand Pressure on the Sky-Lantern Sea side.
The pressures of the two seas would not fall upon a person simultaneously.
Crossing straight through the water required Six Thousand Pressure.
Detouring through the Bone Lantern Grotto-Heaven required only Three Thousand Pressure.
Though the pressure requirement was halved, the rules were doubled; to enter from one side and exit from the other, not a single passage permit from either side could be missing.
Small wonder both sides guarded the land apertures so strictly.
What they were fighting over in the Bone Lantern Grotto-Heaven was not just medicinal lands and mineral veins, but also a cross-sea shortcut accessible with merely Three Thousand Pressure.
An Youyu calculated it in his mind.
Entrusting 【Yicunchun】 to harvest it meant waiting three years.
Entering the grotto-heaven himself, he had only One Hundred Pressure.
Within seven days, neither proper path was viable.
The Bone Lantern Grotto-Heaven was clearly right there on the map, yet to him at present, it was even further out of reach than the Sky-Lantern Sea sixteen thousand nautical miles away.
An Youyu did not hurry to leave.
Walking all the way from the Tide Battle Office to South Bridge, he had intentionally touched dozens of old objects: the old railing by the bridge, the cargo tags handed over by the firms, and old ledgers flipped open.
What he heard was either customers bargaining, clerks checking stock, or sailors urging cargo loading; a few left behind nothing at all.
Not a single word was related to Tiger-Head Mushrooms.
An Youyu still did not give up.
Luotu Firm had dealt in Land Goods for many years. The old objects in the shop might have traveled sea routes alongside Land Medicine, and the lingering sounds they preserved might be clearer than what Shopkeeper Xing remembered.
He scanned his gaze around the store before finally settling on several dark brown wallboards behind the chart.
Those wallboards were not the common wood ray planks found in Seven-Masts.
On the wood surface exposed along the edges of the chart, concentric rings of natural grain interlocked tightly; despite absorbing years of sea tides, it had neither swollen nor cracked.
At a glance, it was clearly 【floatwood】 shipped out from a Sunken Land Grotto-Heaven.
This timber was very light, water-resistant, and far sturdier than wood ray planks. Only fine cargo ships making long cross-sea voyages were willing to spend on building vessels with it.
On the floatwood planks sticking out beneath the chart, holes left from pulled ship nails remained, with blackened pitch solidified in the seams.
This was old hull plating dismantled from some cross-sea merchant ship.
An Youyu did not say a word. Pretending to inspect the wood grain, he brushed his hand across one of the nail holes.
The sounds inside the merchant firm abruptly receded.
The scraping of heavy objects sliding across a deck, chaotic footsteps, and the snapping of ship planks crashed out simultaneously from deep within the floatwood.
———— Lingering Echoes of Old Objects ————
The ship hull seemed to be listing.
Someone bellowed hoarsely amidst the chaos:
"Soil Box Number Three is still locked to the cabin rack!"
"Two Tiger-Head Mushrooms, both inside!"
Immediately after came another grating snap of fracturing wood.
The surroundings suddenly fell quiet for a moment.
Amid heavy, ragged breathing, someone spoke in utter disbelief:
"The ship is sinking!"
"Wait, it stopped again..."
———— Echoes Cut Short ————
An Youyu's heart thumped heavily in his chest.
Coming up empty all along, it was only at this moment that he finally heard the words "Tiger-Head Mushroom."
He paused for a breath before confirming he hadn't misheard.
Soil Box Number Three.
Two Tiger-Head Mushrooms.
And a ship that sank halfway down, only to suddenly stop.
As long as he found out where this hull plank came from, he could still trace this severed medicinal trail.
An Youyu asked, "This wall—was it made from old ship planks?"
Shopkeeper Xing was somewhat surprised. "You recognize floatwood?"
"I used to make a living on independent vessels."
Shopkeeper Xing looked down at the donation slip.
【Clown Float-Commune】.
【New Residency】.
Clown had always been willing to take in victims of shipwrecks with nowhere else to go.
Matched with An Youyu's comment about having worked on independent vessels, his background made sense.
Only then did Shopkeeper Xing look up at the floatwood wall.
"More than ten years ago, a vessel delivering goods for Luotu Firm went missing. It was called the 【Green Bud】, an off-domain land-harvesting merchant vessel meant to deliver a batch of Land Medicine to our firm. The search-and-rescue team brought back a few cracked floatwood planks. They were useless for ship repairs, but throwing them away would be a waste, so we used them to mend this wall."
"Where did the rescuers retrieve these planks from?"
Shopkeeper Xing's gaze moved from the floatwood wall back to An Youyu's face.
"You came looking for medicine, so why are you interested in a shipwreck from over ten years ago?"
"Seeing where someone else's ship broke makes it easier to avoid the same trap in the future."
Shopkeeper Xing nodded. "That makes sense. Anyone who runs ships asks a few extra questions when they hear of a wreck."
"Southwest of Seven-Masts."
"【Wreck Hollow】."
...
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