Zhang Nu returned to the Darkness City, where the main city was gradually bustling with activity.

The city's infrastructure had been improving, attracting more and more people. It was now a hub of opportunities, whether in terms of production or employment.

For instance, there were three advanced farms in the Darkness Valley.

The Goblin Farm, the first and largest among them, had expanded its operations and employed a staggering fifteen thousand goblin workers. These goblins were relocated from goblin villages near Giantree City, Berserk Beast City, and the Darkness Valley.

The Goblin Town within the Darkness City had transformed into the largest goblin utopia in the forest.

It was astonishing to see how a seemingly insignificant and inferior race like goblins could generate millions of gold's worth of production value every day.

The goblin population had become an essential part of the city's economy and development.

However, even with fifteen thousand goblins, they could only fully develop one Level 4 Spirit Field Farm and were unable to handle the establishment of two new farms.

The Demon King had no choice but to recruit skilled planting races from the forest or directly transfer elven planting experts from Giantree City.

Due to the allure of the Ancient Elven Sanctuary, five thousand elves had already relocated to the Darkness City within a few days.

The gnomes from Thousand Fangs City and the dwarves from Ironheart City also decided to send a portion of their people to the Darkness City to facilitate production.

The Demon King's territory extended beyond Giantree City, Berserk Beast City, Thousand Fangs City, Ironheart City, Silver Spring City, Magi Mojo City, and Thunderclap City. It encompassed dozens of medium to large tribes and hundreds of small tribes and villages.

Each tribe consisted of various races, ranging from the powerful tigerfolk, bearfolk, wolffolk, orcs, minotaur, boarfolk, lizardfolk, snakefolk, to the weaker goblins, kobolds, fox-kin, rabbit-kin, and sheepfolk.

There were almost all races and tribes imaginable under the Demon King's command.

The main city was currently accepting applications for citizenship, as the Demon King planned to create the first-ever city that combined multiple environmental and terrain structures to accommodate the coexistence of various races.

In the near future, as long as they were citizens or dependents of the Demon King, regardless of their background or origins, as long as they met the criteria, they could apply to join the Darkness City.

Zhang Nu firmly believed that the Darkness City would prosper soon.

During the process of conquering Thunderclap City, Zhang Nu obtained quite a significant harvest.

He brought back over 14 million gold alone.

The earning capabilities of each major territory and business were also continuously increasing. 

Currently, the combined net profit from various production activities, hunting expeditions, and commercial ventures amounted to approximately one million gold per day.

In other words, even if they did nothing, they would still earn millions of gold coins every day. This was the advantage of expanding territory and increasing the size of their forces.

However, Zhang Nu was well aware that this was far from the end. The potential for future growth was much greater than the current income.

For example, the newly subdued giants.

They cleared monsters in the daemonic lair and hunted nearby magical beasts every day. Even while ensuring their own safety, they could bring in net profits of at least several hundred thousand gold per day.

Another example was elven farms in Giantree City, the application of Thousand Fangs City's gnome magitek, and the dozen large-scale mines awaiting development in Berserk Beast City.

Lastly, there was the expansion of new markets by the Shadow Dragon Chamber of Commerce.

If the Demon King successfully integrated and fully developed these resources while successfully accessing the external markets, earning a mere one million gold per day would be an understatement. It could easily be multiplied tenfold or more.

This fixed income was earned passively, unlike grinding monsters in dungeons.

Stable and reliable.

Zhang Nu checked and found that he currently had nearly 20 million disposable gold.

He decided to continue purchasing blueprints and resources from the major Demon King Markets while conducting a new round of construction and recruitment in his territories.

First and foremost, he planned to upgrade the castle. One of the greatest rewards he obtained from Thunderclap City's reward chest was a castle upgrade scroll.

[Upgrade the Demon King Castle? The upgrade costs "Advanced Castle Upgrade Scroll" x1, "gold" x1.5 million, "dark gem" x1000, "wind, fire, water, earth gem" x200 each, quality iron x20,000, quality stone x20,000, quality wood x20,000!]

After looking at the required materials, Zhang Nu realized that this upgrade would not come cheap, mainly due to the significant amount of gems needed. According to the current market prices, just a thousand dark gems alone were worth at least 2 million gold!

However, it did not matter.

As a Great Demon King, he had an abundance of wealth. Compared to the benefits of castle upgrading, this expense was negligible. What's a little expenditure compared to the advantages of upgrading the castle?

[Castle upgrade successful!]

[Congratulations. You've gained Demon Dragon Castle!]

[Demon Dragon Castle] All territory's production +100%. Within a radius of 100 kilometers from the castle, all units' stats +70%, aging speed -50%, recovery speed +50%, training speed +100%. Within the castle, space +50%, Demon King's recovery speed +300%, stats +100%. Heroes who enter the castle, stats -35%. Gained dual-layered castle barrier.

Almost instantly after the upgrade was completed, all the Demon King units received a brand-new buff.

"My power has increased!"

"My fatigue has disappeared!"

"Oh, my training speed and recovery speed have improved. What's happening?"

"Stupid! Of course it's the blessing of the Demon King to the citizens of the Darkness City!

"The Demon King is truly mighty!"

"Long live the Demon King!"

"......"

Indeed, there was a reason for its high value.

The amplification effect of the Demon Dragon Castle was on par with that of the Tree of Miracle. Moreover, compared to the effects of the Tree of Miracle, which only benefited the elven race, the castle buffs in the Darkness City were for everyone.

Once they arrived in the Darkness City, their power would instantly skyrocket. Various attributes would significantly increase.

Furthermore, there were additional benefits such as increased lifespan, accelerated training speed, and improved production efficiency.

This city, crafted by the draconian, would truly live up to its reputation.

Buffs were everywhere to begin with. Every building, even the squares and roads, had special effects.

Now, with the castle's amplification, it could be called a city of miracle buffs. For the native residents, each citizen qualification was a tremendous blessing.

Aside from the enhanced functionality, the Demon King's castle underwent significant changes. The location of the castle suddenly rose by 500 meters. The entire castle took on a more majestic and oppressive appearance, with its various facilities more perfected, as if tailored specifically for Zhang Nu.

"Not bad!"

Zhang Nu stood on the castle balcony, taking in the entire Darkness City and the entire Darkness Valley below. The feeling of reigning over the world and overlooking the land was satisfying.

After upgrading the castle, Zhang Nu proceeded to use another blueprint obtained from the reward chest of the Thunderclap City.

This blueprint corresponded to a building called the "Tower of Lost Trials". It was indeed a mysterious structure, but it seemed far from simple.

After paying a hefty fee, the trial tower emerged within the city.

Zhang Nu immediately used his cheat ability to carefully examine the relevant information.

The purpose of this trial tower was very simple.

It allowed his subordinates to enter and undergo trials. There were risks involved in these trials, including the possibility of casualties. However, if the trials were successfully completed, the increase in strength would be remarkable. There was even a chance for low-level units to directly evolve into high-level units.

For example, Zhang Nu could send a group of ordinary combat units to undergo the trials. Although there might be some casualties, a portion of the ordinary soldiers could directly upgrade to high-level units through the training during the trials.

It was a cultivation artifact, a building that could consistently produce advanced units.

Although it was not as quick and convenient as manual upgrades, the overall cost was much lower than direct upgrades.

For high-end units, such as the native powerhouses at the lord and overlord ranks, the Tower of Lost Trials could also serve as a sacred place for rapid training.

Despite the risks involved, the potential gains outweighed the risks.

After understanding the effects of the trial tower, Zhang Nu realized that it would be extremely useful for the territory. However, there were two limitations to the trial tower.

The first limitation was that a maximum of only one hundred trials could be conducted per day.

The second limitation was that as a Level 4 building, it could only accept challengers up to Level 4 overlords. Those beyond this level, such as the Demon King, Elven King, and giant chieftain, would not be able to participate.

Although it was somewhat regrettable, Zhang Nu still felt that building the trial tower was highly worthwhile. It would save a significant amount of gold, allowing his units to evolve on their own and accelerate their training speed.

As time went on, the value it created would only increase.

After completing the upgrades and construction in the territory, Zhang Nu began considering adding new unit types to the territory. However, summoning high-level units required the consumption of souls.

While Zhang Nu thought about upgrading Zhang San and Li Si to become Earth Drake Sovereign and Sky Drake Sovereign, the cost was too high, and it was not the right time yet.

In the end, Zhang Nu's attention was drawn to a brand new unit unlocked by the Level 5 advancement, the Abyssal Dragon.

This new Level 5 unit belonged to the same subspecies as Zhang Nu.

Zhang Nu glanced at the summoning requirements.

[Abyssal Dragon] Level 5 overlord. Costs 4 million gold + 1 Level 5 Hero's soul.

The price was actually not expensive. The main issue was the high requirement for souls.

Although Zhang Nu had a considerable reserve of souls, it was not enough to fully awaken any of his Level 5 talents. However, it was more than enough to summon a dragon.

After some thought, Zhang Nu took out six Level 4 souls and synthesized them into a Level 5 soul at the Soul Altar.

Zhang Nu expended the soul and gold coins to summon an Abyssal Dragon!

"HWOOOOAAAARRR---!"

A fierce dragon aura burst forth from the Demon King's Altar, leaving the draconian soldiers guarding the area in awe.

In the next moment, accompanied by a teleportation light, a majestic dragon over 80 meters long, covered in pitch-black scales, appeared upon the altar.

Zhang Nu immediately checked its attributes.

[Abyssal Dragon] Level 5 overlord. 

......

Skills: Draconian Form (Talent), Abyssal Dragon Flame (Talent), Lightning Control (Talent), Dragon Fear (Talent), High Anti-Magic (Talent), Dark Dragonic Tongue Magic (Talent), Dark Invasion (A Rank), Dark Devour (A Rank), Black Hole of Death (A Rank), Undead Creation (B Rank), Shadow Stealth ( B Rank), etc...

Description: This is a mature Abyssal Dragon of the dark element, possessing innate powerful dragon flame and thunder abilities, as well as exceptional talent in dark magic, making it extremely formidable in combat...

Zhang Nu was amazed to discover that this dragon possessed five same innate talents just like himself.

However, the Abyssal Dragon lacked the other talents that Zhang Nu possessed, such as Abyssal Devouring, Evil Dragon's Descent, and Adamantine Dragon Body.

It seemed that Abyssal Dragon Flame, Abyssal Lightning, Dragon Fear, Draconian Form, and High Anti-Magic were the standard first-tier talents for Abyssal Dragons, possessed by almost all of them. But the higher-tier talents were missing in these dragons.

Furthermore, it appeared that Abyssal Dragons had variations in their attributes.

The Abyssal Dragon summoned by Zhang Nu had random attributes.

This particular Abyssal Dragon had pitch-black scales, other than the five major dragon talents, it also had the talent of "Dark Dragonic Tongue Magic," indicating its mastery of dark magic as a black dragon.

"Greetings, my Lord!" The Abyssal Dragon immediately flew down from the altar, its massive and majestic body bowing in submission.

Zhang Nu said, "From now on, you shall be called Long Yi!"

The Abyssal Dragon immediately replied, "Thank you, master, for bestowing me a name."

The first dragon was thus named Longyi. There was no limit to the number of dragons that could be summoned. If more dragons were summoned, they would be named Long Er, Long San, Long Si, and so on.

The Demon King was quite satisfied with his Abyssal Dragon.

This dragon possessed formidable strength, at least reaching the peak overlord. It was capable of contending against monarch level beings for a certain period and was undoubtedly a super elite force at the moment.

With a little training, such as undergoing a few baptisms, there was a possibility of a breakthrough in the future.