Conquering the Citadel of Eternity was no small feat. The quality of monsters here was exceptionally high, even though the scale was somewhat smaller compared to the Malevolent King's tomb. However, the gold rewards were not far behind.
Defeating around two hundred and some magitek guardians netted him 3.5 million gold. From the Immortal Subject Number 0 to Number 10, all of which were at least Level 5 lords, they garnered a total of 23 million gold. In total, just from defeating monsters, he earned approximately 27 million gold.
Zhang Nu then opened the reward chest he obtained.
[You opened the Diamond Treasure Chest. You've gained "Gold" x10 million, "Blueprint: Spirit Sanctum" x1, "Eternal Consciousness" x1, "Spirit Gem" x5,000, "Soul Gem" x5,000!]
There was no doubt that the Citadel of Eternity's formidable challenge had yielded some pleasantly surprising rewards. Although he only received one blueprint this time, it was an invaluable Level 5 special structure blueprint.
[Blueprint: Spirit Sanctum] Level 5 blueprint. Costs gold x50 million, spirit gems x10,000, soul gems x5,000. You may construct a Spirit Sanctum within your territory.
There was no doubt that any Level 5 structure came with an extremely high value. Considering this was a Level 5 special structure, the construction costs were extraordinarily high. Even among Level 5 structures, it was at least ten times more expensive than the average one. Compared to special buildings of the same tier, it was over three times as costly.
Up to this point, among all the blueprints Zhang Nu had acquired, only the Resurrection Altar came close to matching the cost of the Spirit Sanctum. The construction cost of the Resurrection Altar included not only 500 million gold coins but also a vast quantity of Spirit and Soul Stones, along with the consumption of ten Fifth-Tier Souls. It was truly an exorbitant price.
However, the Demon King's Resurrection Altar's power was unmatched. Once constructed, it theoretically granted immortality not only to the Demon King but also to all those under his command, even common foot soldiers. As long as the altar remained, as long as there were sufficient resources, and as long as it was deemed valuable, individuals could be resurrected time and time again, without limit.
Such an incredible ability more than justified the high construction cost of the Resurrection Altar. Yet, what about the Spirit Sanctum? What made it so valuable, and why was its price so steep?
Upon scanning through its information, Zhang Nu learned that the primary function of the Spirit Sanctum was quite straightforward. It could construct an immensely vast spiritual network that allowed all those bound by its contract to enter. The spiritual world built by the Spirit Sanctum was boundless, entirely virtual, and filled with creative potential. Regardless of their physical locations or races, anyone who bore the contract imprint of the Spirit Sanctum could enter this realm at any time.
On the surface, this might not seem overly useful. However, with a bit of consideration, it became clear how valuable it truly was. It was essentially an otherworldly version of a super internet. The value and productivity boost of the internet in the previous world were immense. Thus, the Spirit Sanctum's potential value was equally tremendous. Its capacity for creativity and innovation was disruptive and revolutionary.
This extraordinary building, beyond its primary function, possessed several additional abilities that could only be fully understood once it was officially constructed.
For Zhang Nu, this blueprint was more than satisfactory. This trip had been worthwhile even if Zhang Nu had not gained anything else. Just obtaining this super blueprint was enough to consider it a successful venture.
However, there were still some regrets. This time, no blueprints of magitek structures or facilities had dropped. Zhang Nu only had a Level 3 Magitek Research Institute. Although it had been in use for a short time, it had already yielded quite a few results. Obtaining more magitek facilities, such as a magitek manufacturing factory, a weapons factory, or a unit barracks, would greatly benefit the territory. Nevertheless, one should not be too greedy. It was impossible to stay lucky every time.
Zhang Nu noticed that among the spoils of war this time, there was an Eternal Consciousness. It was a bit of a mixed blessing. The Eternal Consciousness was a cutting-edge technological marvel of the magitek empire, equivalent to a super artificial intelligence in this world. Zhang Nu took out the Eternal Consciousness, which was still trapped in a crystal sphere.
Zhang Nu asked, "Can you hear me?"
"Of course," replied the Eternal Consciousness. "My master!"
The Eternal Consciousness did not hear in the conventional sense, as it did not have ears. Instead, it sensed mental fluctuations, directly interpreting the thoughts of others and transmitting its own thoughts through psychic waves. In Zhang Nu's mind, he heard a crisp, childlike voice. Although devoid of emotion, it was clear and pleasant.
Zhang Nu commanded, "From today, I'll call you Xiao Tong."
"Yes!" Xiao Tong, the Eternal Consciousness, responded. "What can I do for my master?"
The mind of these spiritual entities and artificial intelligences, obtained from the reward chest, were imprinted with absolute loyalty and obedience to the Demon King. They would proactively assist the Demon King in executing any will and command.
Zhang Nu asked, "Can you control this citadel?"
Xiao Tong replied, "I believe I should be able to."
The central control of the Citadel of Eternity used to be an Eternal Consciousness. If the 1st Eternal being could control the citadel, there was no reason why Xiao Tong couldn't.
Zhang Nu placed Xiao Tong on the central control console. In the next moment, he clearly sensed the entire Citadel of Eternity rapidly rebooting. The citadel was equipped with numerous mental amplification arrays that could amplify Xiao Tong's psychic power by hundreds or even thousands of times, granting her enhanced perception and computational abilities.
At this moment, Xiao Tong's sensing range covered almost the entire citadel. Simultaneously, Zhang Nu received a notification:
[You have obtained a Level 5 special building "Supreme Magitek Floating Citadel"!]
Upon receiving this notification, Zhang Nu was left in disbelief. It was the first time he had obtained a building without constructing it himself. Apparently, Demon King buildings and facilities didn't necessarily have to be built by the Demon King personally; obtaining them from enemies or relics worked just as effectively. However, such circumstances were exceedingly rare.
Zhang Nu asked, "What is the current operational status of this citadel?"
Xiao Tong replied, "Reporting to the master, this is a large-scale floating citadel with 72% of its components experiencing malfunctions. Most of its combat weapons are nonfunctional, and its floating and void propulsion systems cannot be activated. It requires extensive repairs before it can be fully operational."
Zhang Nu had not expected the damage to be so severe, but it was also unsurprising. The Magitek Citadel had been abandoned for an extended period. If not for the continuous maintenance by the 1st Immortal Subject, it would likely have turned into a scrap heap long ago.
Nonetheless, Zhang Nu was elated. To come across a Level 5 special building like this for free was a significant boon. This was a super citadel constructed during the peak of the ancient magitek empire. It was not just a massive laboratory but also a super magitek floating base that combined functions such as research, production, and military capabilities.
The Citadel of Eternity had the ability to float and move. It could be deployed to any location. Zhang Nu had been concerned about not having a robust fortress or defensive line during his confrontations with the empire. If he could repair the Citadel of Eternity, he could simply place it on the front lines, becoming an impregnable stronghold.
Furthermore, unlike traditional citadels, the Citadel of Eternity could be equipped with massive magitek weapons to create a network of firepower. It could adapt to changing battlefields by moving wherever needed, always dominating the front lines. It was indeed a nightmare for the enemy.
With this fortress, the Demon King had acquired a strategic advantage akin to having a thousand armies. The Citadel of Eternity was not only a powerful magitech fortress but also had comprehensive production and research facilities, enhancing its value in those areas.
"I need to find a way," Zhang Nu thought. "I must repair the citadel as soon as possible."
While the draconians possessed excellent construction skills, they were unlikely to be able to repair the Citadel of Eternity. The gnomes of Thousand Fangs City had some knowledge of magitek, but restoring the Citadel of Eternity would be nearly impossible unless they spent three to five decades on it.
After careful consideration, Zhang Nu concluded that he needed to acquire a Restoration Scroll from the Demon King's market. Restoration Scrolls were rare items in the Demon King's arsenal, similar to Upgrade Scrolls, but they were specifically designed for repairing Demon King buildings. As the name suggested, they were used for restoration, whether it was a regular building, a special building, or a core structure like the Demon King's castle. However, restoring a building required the appropriate materials, and the scrolls came in different grades. To repair the Citadel of Eternity, Zhang Nu needed a Level 5 Universal Restoration Scroll, which would not be easy to come by. It all depended on luck. As long as he could afford the price, he would eventually find one, but there was no telling how long this would take.
In summary, Zhang Nu had a bountiful harvest from this expedition. He returned to the Darkness City with a sense of satisfaction. He had acquired a substantial amount of gold, spirit gems, and soul gems. With these resources, Zhang Nu could consider constructing either a Resurrection Altar or the Spirit Sanctum. Both of these structures were crucial and immensely powerful, so they needed to be built.
However, at the moment, he did not have enough gems. Zhang Nu could only afford to construct one of them. After careful consideration, he decided to prioritize building the Spirit Sanctum. This choice was influenced by the fact that the Resurrection Altar required an enormous amount of soul gems, a whopping ten thousand, while Zhang Nu had only acquired eight thousand in this operation. Soul gems were rare and expensive, making them challenging to obtain.
The location for the construction was an easy decision for Zhang Nu. He chose to place it right beside the Demon King's Altar. Being qualified to be located next to the Demon King's Altar meant that this building was considered a core facility by the Demon King. In practice, this was indeed the case.
Once the Spirit Sanctum was constructed, the Demon King would effectively possess a vast spirit-powered internet. This would allow him to better control each of his subjects. Furthermore, it would significantly reduce space and time costs for the Demon King's territory and subjects, greatly improving various efficiencies in intelligence circulation, business production, and even entertainment. These changes would be unprecedented and might become one of the core competitive advantages of the Darkness City in the future."