The whole nation is trying to survive on the cable car; I'm choosing one of three options at ea

[Research level has reached Lv10, unlocking spell card slot (Lv1). Unlock requirement: Have previously defeated a level 5 or higher purple-tier monster (completed).]

[Spell Card: Building Rage (Lv1)...When activated, all cable car buildings gain a 50% increase in attack speed and attack power for 10 minutes. Cooldown: 3 days.]

Su Mu's eyes lit up slightly as he looked at the description.

With a 50% increase in attack speed and attack power, the damage output within these ten minutes can at least double.

The only condition for unlocking this spell card is reaching a research level of ten; there are no prerequisites. In other words, as long as you accumulate research materials, you can get a new spell card for free every ten levels.

The appearance of spell cards raised Su Mu's expectations for the research system considerably, but when he opened the next level of the research interface, the reward slots that had not yet been unlocked were still grayed out... He could only see the words "Unlock condition: Research level Lv20". As for what spell cards would be obtained, the panel did not reveal a single word.

More importantly, the upgrade costs have increased. The requirement for the next level has jumped from 10 research materials to 20.

Given the weekly purchase limit of 100, even if he buys all the research materials every week, he would still need to wait at least two weeks after the settlement to have enough materials to try and see the Lv20 reward.

"Two weeks..." He kept this timeframe in mind.

As for the remaining 20,000 arena points, he didn't exchange them for research materials... The exchange channel has a weekly purchase limit of 100, and he had already used up his weekly limit, so he couldn't buy any more. He could also obtain other materials by defeating monsters and through the exchange, so exchanging them with arena points wasn't cost-effective. He would save the points for later and consider it after the purchase limit refreshed next week.

Su Mu switched the panel to the backpack interface and glanced at his current Ghost Crystal balance... more than three thousand eight hundred.

This amount would be a huge sum on any cable network. The purchase price of one Mysterious Crystal on the World Exchange has risen to 1,200 World Coins, so 3,800 crystals would be equivalent to more than 4.5 million World Coins.

But Su Mu had no intention of selling them. The situation ahead was unclear, and he wanted to convert all of these strange crystals into combat power.

He closed the research panel and turned his attention to the arrow tower.

He walked to the side wall of the cable car, opened the external weapon interface, and his gaze fell on the two arrow towers... the main arrow tower was level three, and the backup arrow tower was level one.

He had used these two arrow towers for a while before, but because the supply of arrows couldn't keep up, he didn't upgrade them much afterward.

Now that there's a world exchange, arrows can be purchased in bulk, which fills this gap. Furthermore, once the cable car is upgraded to level five, arrow tower upgrades can be completed directly with Ghost Crystals, eliminating the need to acquire blueprints and materials.

Su Mu first opened the upgrade interface for the main arrow tower.

【小型连弩箭匣（Lv3）→ Lv4：消耗诡晶×600。升级效果：範围溅射伤害，攻击命中后对目标周围5米内的敌人造成35%的溅射伤害。】

He clicked confirm. Six hundred Ghost Crystals were swiped from the account, the main arrow tower's level jumped to level four, and the attack power on the panel increased from over sixty to over one hundred. Next came the requirement to upgrade to level five.

【Lv4 → Lv5：消耗诡晶×1000。升级效果：快速射击（射速提升30%）+穿透射击（每次攻击可穿透3个目标）。】

Su Mu clicked "confirm" again. One thousand strange crystals disappeared, and the main arrow tower's level jumped to level five. He brought up the attribute panel and glanced at it:

Main Arrow Tower (Level 5)

Base firepower: 220

[Attack range: 500 meters]

【特殊效果：燃烧箭（20%概率灼烧）、溅射（5米範围，35%伤害）、快速射击（射速+30%）、穿透射击（穿透3个目标）】

The base firepower of the 220 is already quite impressive at this stage, nearly ten times higher than that of his M500.

If splash damage and penetration are taken into account, a single arrow fired into a dense horde of monsters can deal far more damage than the displayed value. He then spent the same 600 and 1000 monster crystals to upgrade the spare arrow tower from level one to level five.

The two level-five arrow towers cost a total of 3,200 Ghost Crystals, leaving a balance of over 600 in the account. He doesn't plan to touch these for now, saving them for emergencies.

The two arrow towers were slightly adjusted in their mounting slots, and a light blue sheen appeared on their surfaces, indicating that the upgrade was complete.

Su Mu closed all the panels and walked back to the window.

The fighting on the city wall continued, but the situation had changed. The black spots on the golden curtain had more than doubled in size, and visible cracks had appeared in the thinnest parts.

Smaller, eerie creatures squeezed through the cracks and engaged in a chaotic battle with the monsters inside the city on the open ground inside the walls. The corpses of giants and minotaurs were piled up everywhere, and dark green blood flowed in streams down the cracks in the ground.

Those who descended from the sky remained by the tower, and no one crossed that invisible boundary.

Su Mu noticed that when the strange creatures approached the area where they were, the white light at the top of the tower flashed, and the creatures' bodies seemed to be burned by something, and they suddenly shrank back.

"The area around the tower is safe." Su Mu noted this observation in his mind.

Further away, deeper into the city, Su Mu noticed some even larger silhouettes... These things did not rush towards the city walls, nor did they participate in the battle on the front lines; they simply crouched quietly among the ruins, as if waiting for something.

They were several times larger than the giants near the city walls, and Su Mu could see their blurry outlines even from a kilometer away.

As for the strange creatures pouring in from outside the city... although there were many of them, they were all small, low-ranking grunts. None of the truly terrifying behemoths, those comparable in size to chimeras, entered the city.

They simply stood at the edge of the city wall, as if waiting for the golden curtain to completely shatter before taking a step forward.

Su Mu withdrew his gaze and opened the chat channel.

The messages are still rolling.