After leaving the survivor settlement, Su Yao and Ling Yu headed towards the key location indicated in the information. The journey became increasingly difficult, with the ground covered by a thick layer of ice, and the sound of ice cracking echoing underfoot from time to time, as if it were a warning from this apocalypse.

They traversed an ice field dotted with enormous ice pillars of various shapes, some resembling grotesque monsters, others twisted human figures. Suddenly, Su Yao's system issued an alarm, warning of energy interference in the surrounding area, and her vision began to blur.

Just then, a group of ice knights clad in ancient armor emerged from behind the ice pillars. These ice knights rode warhorses also made of ice; their eyes were empty, yet they radiated a chilling killing intent. The ice knights raised their ice swords and charged towards Su Yao and Ling Yu.

Ling Yu immediately used his ice-based ability to create an ice wall in front of him. However, the ice knights' warhorses easily leaped over the ice wall and continued their charge. Su Yao activated her spatial wind blades, which struck the ice knights, only sending up some ice shards and causing no real damage.

Su Yao realized that these ice knights were controlled by some ancient power, and ordinary attacks would be ineffective. She focused her mind and used the system to scan the energy source of the ice knights, discovering that their power core was in the stirrups of their warhorses.

She relayed this information to Ling Yu, and the two began to change tactics. Su Yao used spatial teleportation to avoid the Ice Knights' attacks while simultaneously approaching their warhorses. Ling Yu, on the other hand, used his ice-based abilities to create ice spikes, which he fired at the Ice Knights' warhorses in an attempt to damage their stirrups.

In the midst of the fierce battle, Su Yao successfully teleported next to a warhorse and attempted to pull off the stirrups using her spatial abilities. The Ice Knight noticed her intention and swung his sword at her. Su Yao teleported away in time, and the stirrups cracked under the strain of her spatial abilities.

Taking advantage of the situation, Ling Yu shot the stirrup with an ice spear imbued with powerful energy. The stirrup shattered, and the ice knight and his warhorse instantly turned into ice. They used the same method to defeat the ice knights one by one. After dealing with the ice knights, they continued on their journey.

After a long trek, they arrived at an ancient castle surrounded by ice and snow. The castle gates were tightly shut, and the walls were covered with sharp ice spikes. Su Yao's system indicated that the key location was inside the castle.

They searched for an entrance around the castle and found a small door covered by ice and snow in a corner of the wall. Su Yao used her spatial abilities to clear the ice and snow, opened the small door, and entered the castle. The castle was gloomy and cold, with some tattered flags hanging on the walls, their patterns blurred and indistinct.

In the castle's hall, they encountered a group of ghostly ice maidens. These maidens moved swiftly, holding ice candlesticks that emitted a chilling light. Upon discovering Su Yao and Ling Yu, the maidens began to let out shrill screams that echoed throughout the castle, sending chills down their spines.

Su Yao activated her wind blade ability, but the wind blades passed through the maid's body without causing any damage. Ling Yu's ice-based attack was also ineffective. Su Yao discovered that these maids attacked using sound; their screams could drastically lower the surrounding temperature and even freeze objects.

They covered their ears, trying to block out the maid's screams. Su Yao came up with an idea; she took out some soundproofing materials she had collected earlier from her spatial storage and made simple earplugs. After the two put on the earplugs, the maid's screams had a much smaller impact on them.

Su Yao used her spatial ability to snatch the ice candlestick from the maid's hand, causing the maid to panic. Ling Yu then used his ice-based ability to condense the surrounding moisture into ice beads, which he then shot towards the maids. After the ice beads struck the maids, their bodies began to dissipate.

After dealing with the Ice Maid, they continued their exploration within the castle. In the castle's basement, they found a massive energy device surrounded by intricate runes and circuits. Su Yao's system began analyzing the device, which was likely the core mechanism controlling the extreme cold of the apocalypse, but activating it required solving complex puzzles and finding the corresponding energy key.

They searched the basement for clues and discovered ancient texts and patterns carved into the walls. Su Yao used the system to record and translate this information, hoping to find a way to solve the puzzle and find the energy key—a crucial step in changing their fate in this apocalyptic world, and they had to give it their all.