The Decrypt Underworld

"I don't want to!" Aura complained and wrapped her limbs and tail around Styx in a vice-like bind.

Styx lay on the ground, unable to move as he was completely restrained under the irresistible strength of the Monster Lord.

"Aura, I need you to go with the expedition team."

"Make that spider go!"

"You are better suited. Your strength is offensive, whilst hers is mostly reactive. Also, her threads are full of mana, which would greatly cripple her strength."

"…"

"You have also been working on consuming mana, right? This will be the greatest strength against those husk like monsters."

Styx tried to wriggle in her grasp, but his efforts were in vain.

Aura had previously been occupied watching all of Styx's production lines, which had expanded again.

Raw materials entered on full T3 Conveyer Belts and were pulled off by T3 Item Pickers. The T3 versions of these mana devices were the same design as the previous T2 counterparts, but had been further optimized, becoming more efficient and less prone to error as the technology matured.

The new facilities were creating logistics products. A large section of it created train track lines, whilst another created support beams. Another more specialized facility would produce the various components and assemble carriages.

As Styx expanded more, he needed to increase his logistics capabilities. He opted to follow the original method of the human civilisation and introduce trains.

Giant bored out tunnels would be lined with these train tracks and have loading and unloading facilities at each stop. Each tunnel could support a maximum of four trains at once, but only two could be loaded or unloaded at once.

There was no engine or driving compartment though. Styx also didn't want to manually control them either, so it was all built into the train tracks.

The train tracks were in fact possibly Styx's greatest invention yet. The reason being was that it was first the power source for the train, they had an interconnected mana line which would travel through them, with the stations and other mana generating nodes.

This wouldn't allow the train to move overly fast until the entire tunnels could be filled with ambient mana and take over as the main driving power, but it was enough to make the system functional.

On a deeper level within the tracks was a feat of mana engineering that left Styx feeling highly narcissistic. The Horönheim magic system was one based on logic more so than those like the demon's magic system that was much more intention based.

Styx used it to create a logic system for automatically controlling the trains. One station or logistics point would request items, and it would first search for an empty train, or "queue" the request.

That train would then be directed by this network of magic circles to pick up cargo where it is available and deliver it to the requested point.

They worked as a signalling system for the trains, while also controlling the track changing systems.

This was important because Styx's dungeon was primarily underground, and trying to maintain above ground tracks would be much harder. Monsters or the now wandering demon tribes were also less likely to attack his trains or related infrastructure while they were underground.

The knowledge he had gained from the fallen world had helped fuel a lot of his progresion. The train carriages had space expansion and several other skills "grown" in them.

Styx was convinced there was a treasure trove of knowledge still lurking inside there, he just had to find it.

Heaven had attached a lot of importance to it too and assigned two Fifth Step angels, whilst The Void had caught wind too and send a <Lv. 99> peak Fifth Step ranker of unknown origin to Styx to join the expedition team.

Styx needed at least one Monster Lord of his own there, and Dragon technically wasn't his, so he didn't want to have him step in as a proxy if possible.

~~~~~

⠀

Eventually, Aura released Styx and joined the expedition party. She already belonged to Styx, and would do anything he asked of her. She was simply expressing her frustrations.

This expedition party didn't replace the former, but served a different purpose. The four Fifth Step existences formed the core force and were supported by another ten Fourth Step members of Heaven and The Void.

Ursula was one of them, and she constantly avoided making eye contact with Styx. Loreley would have joined them too, but there was still tension between her and the other members of Heaven. The latter stood beside Styx and looked at the ground in guilt, barely resisting the urge to cocoon herself in her wings.

Styx wanted to grab her in his arms, but he knew doing this before the emissaries of Heaven would only increase her guilt.

This was mainly because the deeper into the fallen world they travelled, the more powerful the enemies became. Any person or monster below the Fourth Step would only serve as food to the mana deprived husks.

The Third Step and below dungeon residents were instead in charge of further exploring the outskirts and uncovering any information or knowledge there. The dungeon wives, Klair and Kale were leading this group this time, and it was a relatively low danger mission according to Styx's calculations.

"Do you understand your roles?" Styx asked the group members, the leading Fifth Step leaders in particular.

"Of course," One of the 6-winged angels, Adam, nodded his head. "We are to delve deeper into the fallen city to investigate the past and recover any lost knowledge."

"Excellent, a copy of that knowledge will be provided to each party to take back to your force. Any questions?"

"The Void wants a copy of the previously spoils," Illidiath, The Void's fifth step emissary that was on the cusp of godhood furrowed her brow, unhappy that their force had been left out previously.

"Bring back enough knowledge for me and I can duplicate some of my knowledge."

"Snort, we want it all, little dungeon."

Illidiath truly had an overbearing presence, even more so than Dragon from what Styx could tell. The woman was extremely beautiful, with long violet hair and a large bust that her clothes tightly clung to.

Fifth Step existences rarely used armor, considering their bodies were not only stronger than the overwhelming majority of metals on the mortal plane, but they could heal from any non soul based damage almost immediately, one of the benefits of having an almost pure mana body.

⠀​Styx looked at her with a gaze of lust and commented, "Of course, but what will you give in return?"

She felt his gaze running up and down her body licentiously and looked at him in disdain, "I'm already <Lv. 99> and don't have to worry about any Max Level bottlenecks, your desire for my body is never going to be fulfilled."

Styx seemed to be petrified as he also just realised that his greatest enticement towards people was useless on this Fifth Step woman.

~~~~~

⠀

Aura and the others in the deep expedition team reached the giant abyssal hole within the city. It seemed bottomless, but that was just because only the smallest sparks of light could escape its depths.

Styx had lent them some flying monsters at the late Second Step. They were weak and worthless for combat here, but they allowed the group to fly without the usage of mana.

"This place is giving me the creeps," Illidiath furrowed her brows and looked into the depths of the hole from the back of her mount. "I can't even contact heaven and have them use their abilities to analyse anything here."

"We will be descending now," Aura parroted Styx's words as they group of elites slowly flew down into the hole.

Aura scrunched her nose as inside was filled with the stench of ash and decay. Styx was surprised as the presence of mould meant there was still some life left over.

'Perhaps it isn't completely dead, but they managed to survive deeper inside by concentrating their resources.'

Styx mused to himself as it was undeniable this civilisation's usage of mana was unparalleled.

As the group went deeper, lights began to show themselves. Along the walls of the chasm, purple iridescent flowers grew on the walls, but most of them were wilted and dead. These were the source of the scent of rot and mould.

Eventually, the tunnel down ended and opened into an entire world. A giant silvery river travelled across the landscape with the occasional murky soul floating down it.

More purple flowers populated the shores of this river and occasionally spread through the craggy ladscape, shedding a light purple glow. There were some old constructions and pantheons, but they had all fallen into disrepair and had collapsed in at least one location.

Spectres wandered across the land, searching for any soul matter or mana to eat. The would suck out the vitality of these flowers just to maintain their existence.

Back in the dungeon, Styx's brows shot up in shock as he recognised this location.

"Isn't this the fabled river of souls!? Does such a thing really exist? Or was it manmade?"

"What is a river of souls?"

Beatrice hugged him from behind and rested her hand on his shoulder.

"What is a river of souls?"

"A concept of the underworld and reincarnation. When one dies, their soul passes through this river of souls where it is cleaned of all memories and worldly sins before being reborn as a new infant."

"So why would it exist in this fallen world, especially somewhere people can simply walk into?"

"It is unnatural. I think… it may have been manufactured to fulfil that purpose, separating those souls from the standard reincarnation cycle."

"Why would they do that?"

"I don't know, but I intend to find out."

"Do those husks go there when they die?"

"No, their souls would be too twisted and tattered. There is nothing left within their bodies except hunger for mana. When they die, their souls are probably extinguished too. The souls the appear to occasionally pass by a quite eroded by constant reincarnation cycles, it mustn't be perfect. But.."

"But?"

"Why are there so little souls? Such a river should be constantly filled with souls seeking reincarnation."