Beneath this fortress lay a maze of long, winding tunnels. They were a bit like a city's sewers, but their purpose was clearly different. City sewers were mainly for drainage, waste disposal, flood control, preventing foundation collapse, and things like that.

The tunnels here were obviously meant to expand living space and provide shade from the sun. This passage might even connect to the outside of the city. It was a hidden move left behind by the human side, practically a full-blown defensive structure.

There were a lot of humans near the tunnel, so Night Frost, with her elf-like appearance, stood out far too much. She put on a cloak, lightened her steps, and moved through the air little by little toward the depths of the passage, trying her best not to draw the underground guards' attention.

Everything went smoothly. The guards never noticed Night Frost in midair. So she sped up a little and swept behind the tunnel at the corner.

Night Frost was starting to think she really needed to learn an invisibility Magic Spell. It really was perfect for infiltration. Back then, when Crimson used that invisibility spell, Night Frost had been insanely jealous. The only problem was that the spell was extremely difficult. Supposedly, before learning it, you first had to learn how to wrap objects in Mana and make them turn invisible.

Well, whatever. Tonight, she'd check out the treasure first. Invisibility and sneaking could wait until later.

The tunnel was pitch-black. Sunlight could still reach this section during the day, so the humans hadn't installed any lighting here. But after walking a little farther, Night Frost saw patterns covering the walls.

Because of those patterns, the long, narrow tunnel became dazzlingly bright. Once she got closer, Night Frost didn't even dare keep her eyes open. It was just too blinding.

After passing through the tunnel, Night Frost arrived in the area where the humans lived. Honestly, this place felt even livelier than the streets above. The stalls here sold gold and silver jewelry, food, and all sorts of things. The whole passage was filled with shouting and hawking.

Though Night Frost couldn't understand a word of it.

After observing the place carefully, Night Frost noticed quite a few sturdy human men. And in one corner of the tunnel, she could even sense fluctuations of Mana...

One look at that shop told her it wasn't anything respectable. The place reeked of something eerie and gloomy. It looked a bit like a Western fortune-teller's shop. Inside, there was probably some creepy old woman hugging a crystal ball, with cloth draped over most of her face, muttering mysterious nonsense.

But Night Frost didn't care about that shop. It wasn't her main target. Besides, she couldn't understand the language here anyway, so it was better not to stir up trouble.

After going around the shop, Night Frost arrived near the wooden crates in the corner. According to the hints and map the Elderly Elf had given her, all she had to do was jump down, and she'd find the path leading to the treasure.

This entrance had been sealed by the Elderly Elf with a Magic Spell. Only someone acknowledged by the Elderly Elf and carrying the token could go down safely. And Night Frost happened to have the token the Elderly Elf had given her.

Night Frost jumped down, falling from light into darkness. There wasn't the slightest bit of light on the road ahead. She tapped her brow and activated her night vision.

The one thing that did make her relax was this: there were no living people down here. Night Frost no longer needed to hide.

"It's really dark..."

Night Frost looked at the blue-glowing Eye Orb. It was already scanning the structure of the tunnel. She waited quietly in place. She wasn't short on time. While waiting, she observed the surroundings—

This was clearly a man-made tunnel. Compared to the intricate passages above, the tunnel here was much rougher, and only one person could pass through at a time.

There weren't any traps in this tunnel. After activating her night vision, Night Frost kept one hand on the wall and advanced carefully. The Eye Orb rested on her shoulder, while Li Dogegg was fast asleep in her familiar space.

"That guy really has it easy."

Night Frost grumbled, but her steps never stopped.

At last, heaven didn't fail the determined. After following the map through dozens of turns, Night Frost finally found an open area. Presumably, this was where the treasure of the people of this realm was kept.

The moment Night Frost took one step forward, she slammed into an invisible wall. The instant her head made intimate contact with it, patterns surfaced across the transparent barrier.

Array Patterns!

Night Frost, who knew this field well, recognized them at a glance. The Elderly Elf hadn't lied. This thing really was troublesome.

From that one collision alone, Night Frost had already seen several different Array Patterns. This was a masterpiece made by blending multiple Array Patterns together. It not only had the toughness and stability of a defensive Array Pattern, but also the effects of several others.

In that instant, Night Frost saw a defensive Array Pattern, a rebound-effect Array Pattern, a reinforcement Array Pattern, and one more Array Pattern she didn't recognize. Those four were woven together, forming the foundation of this grand Formation.

There were also attack, amplification, and corrosion Array Patterns inscribed on the ground. Those were just the visible ones, the ones Night Frost could clearly see. As for the hidden Array Patterns, she'd have to get closer to know.

Night Frost recognized all of these. They were definitely Array Patterns from this realm. There was no need to think further. She could directly conclude that whoever carved this hybrid grand Formation had, without question, come from this realm.

"Hm... this is a bit tricky."

Night Frost frowned tightly. This hybrid grand Formation truly wrapped everything inside it with no blind spots at all. Just the outermost layer alone would take her several days to unravel layer by layer, and that was assuming things went smoothly.

Even if she broke through the first layer, she'd still have to face the second layer, a killing Formation. With attack Array Patterns this advanced, plus amplification Array Patterns, Night Frost didn't even want to imagine its power.

Brute force was out of the question. The rebound Array Pattern inside this grand Formation, along with that unknown Array Pattern, definitely wasn't there for decoration.

The fastest method would naturally be to destroy the Array Pattern's core and wait for the Formation to dissipate on its own. But that core seemed to be hidden in the deepest part, wrapped in another layer of Array Patterns Night Frost didn't recognize.

"Even if I don't know what that Array Pattern is, I can still make out the core if I look carefully. But that core seems to be made of Obsidian Stone... just like the obsidian outside the fortress. Extremely pure."

Destroying the Array Patterns directly seemed impossible. Night Frost could only break them step by step.

"Honestly, the moment I saw these Array Patterns, I almost wanted to give up. There's no way this thing can be cracked in a day or two. It's obvious some absurdly overqualified Formation master from this realm got bored and left their life's masterpiece here."

Night Frost held her carving knife. She wasn't some absurdly overqualified grandmaster. Her understanding of Formations wasn't that deep, either. She spent all day fighting and killing. She wasn't the type who could calmly sit down and study.

She placed her palm against the transparent barrier. Faint patterns surfaced. Night Frost stared at the flowing lines without blinking, quietly waiting for the same pattern to appear again.

As long as the same pattern appeared, that meant the Formation had completed one "cycle," or maybe half a cycle. Just like Mana in the human body, the Mana in a Formation also followed a cycle, returning from the starting point to the end point.

This was Night Frost's usual method for breaking Array Patterns. But this Formation was a little unreasonable. She did find the cycle of one Array Pattern, but only one. The other four were intertwined with it. Breaking the known cycle would definitely trigger the others into violent upheaval.

So Night Frost needed to find the point where the cycles of those four Array Patterns intersected. She had to lock down that intersection first, then break the Array Patterns one by one.

This tiny space was nowhere near enough. If she wanted to undo this Array Pattern, she needed a wider area to move freely. So next, Night Frost had to widen this narrow tunnel until she could move around inside it with relative freedom.

"No wonder that old guy said breaking this thing would take a long time... just excavating the tunnel alone eats up plenty of time."

The Eye Orb, lying in the corner, complained.

"I think he just didn't understand the Array Patterns of this realm. Look, there are scorch marks here. Someone obviously tried to break it before. But clearly, they failed."

Night Frost condensed a Crimson Gold Spear and slowly chipped away at the walls on both sides. The earth and stone here were unbelievably hard. Just excavating them took a lot out of her.

If she blasted everything apart with Mana, it might affect the foundation of the Obsidian Stone fortress. If lives inside the fortress were lost for the sake of treasure, Night Frost would probably feel guilty for quite a while.

"Wait, I just thought of an expert digger!"

Night Frost remembered the bird-type Monsters she had seen when she first arrived in this Abyss. They seemed able to break through hard rock with their sharp beaks and horns. And right now, Li Dogegg was exactly that kind of monster.

So Night Frost shook Li Dogegg awake.

Li Dogegg was furious. Ever since coming to this fortress, it hadn't had a single good sleep. What was it this time? Please don't tell it this was another translation job. Translating all day was seriously annoying for a dragon.

But today, Night Frost really did give it a surprise. Today, she had spawned in an underground mine. It was pitch-black, but Li Dogegg had night vision too, so it could see clearly in the dark.

Then it saw Night Frost point at the wall and say:

"Go, Li Dogegg. Dig this place open!"

Li Dogegg froze on the spot. What kind of nonsense was this?

She wanted it to dig this place out?

It looked at its claws, then at the hard rock wall. It really didn't seem like it had the ability to dig through this.

Night Frost pointed at Li Dogegg's beak and the not-yet-fully-grown horn on its forehead. Li Dogegg seemed to connect the dots. It remembered that the mother of this species really did have the ability to excavate tunnels with its beak and horn. And now Night Frost wanted it to do exactly that.

This was inhuman! It had only been born a few days ago, and she already wanted it doing this kind of labor?! At this rate, translation work would've been better...

Li Dogegg really wanted to protest. But it had signed a contract with Night Frost. Sure, on the surface it was called an equal contract, but the moment it was signed, Li Dogegg understood. Its whole life had basically been sold to Night Frost.

Naturally, protesting was useless. Night Frost dragged Li Dogegg off to mine one side of the rock wall, while she and the Eye Orb worked on the other. With both sides moving at once, progress sped up quite a bit.

But because of working intense night shifts for so long, Li Dogegg gradually developed the habit of sleeping during the day and working at night, perfectly blending into the lifestyle of the local residents.