Reincarnated With The Strongest System

'Are you serious?!' William couldn't believe what the system had told him. 

The job class that he had used in the battle against the Cyclops could only be unlocked if his soul was corrupted by the god of Darkness.

< Host, the Job Class Prince and Princess of Darkness is a Prestige Class that belongs to the devout follower of the God of Darkness. To be honest, it is impossible for you to unlock it. It was only possible because you used the Collar of Wisteria as a medium to sacrifice five years of your magic power to use the Job Class for a short period of time. >

'How can this be?' William was starting to feel helpless. 'What am I supposed to do?'

Oliver noticed the change in William's expression and frowned. "What are you dilly dallying for? Have you switched that Job Class or whatever to Prince of Darkness? Hurry, we don't have much time."

"S-Second Master, the Prince of Darkness is not available," William replied. "I can't use it." 

"Is that so?" Oliver knew that William wouldn't lie to him at this crucial moment so he had no choice but to believe him. "Okay, just switch to the Dark Mage. I just hope that your soul will be able to endure the corruption and the pain. Don't worry, I will assist you. With the two of us together, it will work… probably."

< Host, the cores' corruption has progressed to 98% >

William took two deep breaths in order to calm himself. He knew that he was taking a big risk in attempting what he was about to do, but he had to do it. Something inside him was compelling him to do it. 

What William didn't know was that, deep within his sea of consciousness, the chess piece of the King started to vibrate. The time for it to awaken was still not at hand, but it had sensed William's desire and decided to lend its strength.

-----

Issei, who was napping in the Temple of the Ten-Thousand Gods, felt his divinity start to move and immediately investigated the cause. The only person whom he had given his divinity to was William. Since the chess piece was moving, it meant that his sworn brother had encountered something very troublesome.

'It's still too early,' Issei frowned as he observed William's projection from inside his palace. 'Still, nothing ventured, nothing gained. The greater the challenge, the greater the gains. Goodluck, little brother.'

-----

After changing his job class to the Dark Mage, William prepared himself to touch the two cores with his hands at the same time.

"Listen to me, whatever happens do not lose yourself," Oliver said with a serious expression as he hovered above William's head. "The moment you touch those two cores, the miasma will slam on your sea of consciousness like a tidal wave. You must resist, and keep your consciousness at all costs. If you fail then your body will be corrupted by miasma. Are you sure you're not going to change your mind?"

"No." William shook his head. "I am ready."

"Good." Oliver nodded and spread his wings wide. "Let's start."

William gritted his teeth and touched both cores at the same time. Immediately, the miasma traveled through his hands and up to his arms, instantly turning it black. William felt something slam into the core of his very being as his soul shuddered from the impact.

This was the second time he'd felt something like this. The first time was when the truck appeared in the cycle of reincarnation and sent him flying to be born in this world. The impact had been so strong that it damaged William's soul. It caused him to be unable to regain consciousness for more than a month after he was born.

Fortunately, due to the incident with Truck-kun, William's soul had been strengthened after it had recovered. It was further strengthened by Celine's Hell Training inside his Sea of Consciousness.

Although he wanted to faint from the pain, Oliver's encouragement and his Mama Ella's bleating had reached his ears.

He endured the corruption of the Miasma as his body was slowly being stained black. Some time later, a patch of bright light, the size of a gold coin, appeared in the center of the two dungeon cores. Oliver hurriedly used his powers to pull the souls of the twin cores out from the bodies that were on the verge of collapse. 

It was a painstaking process as Oliver divided his attention between supplying William some of his strength and extracting the souls from the two cores. 

The Two Guardian Beast knew that this was the turning point, so they channeled the remaining power in their bodies into William. They were also doing their best to help the person who decided to save their masters from complete destruction.

The goats had stopped playing with the Orthus, because the Guardian Beast had also regained some of its sanity. It joined its seniors in helping William resist the corruption as its way of atonement.

Right now, William's whole body had been stained black. Even his hair and eyes hadn't escaped the miasma's corruption.

Although it was very painful, the years he had spent being trained by Celine and Oliver ironically helped him endure the torturous ordeal he was currently experiencing. 

Inside his sea of consciousness, William's soul floated above blue waters that were also slowly being stained with the black miasma. In time, the sea had turned completely black. Suddenly a single strand of darkness, as thin as a thread, rose up from the corrupted waters and pierced William's chest.

It wormed its way inside William's soul and successfully infiltrated his core. After that single strand had been absorbed, more strands flew into the air and attempted to pierce William's chest once again. However, a powerful divinity blocked them. 

The chess piece hovered above William's body and shielded his soul from further harm. It had waited for that single strand of darkness to pierce William's chest before it made its move. 

The young boy was not able to resist the single strand of darkness that attacked him because he had already lost consciousness at that point in time. The chess piece could have prevented the incident from happening, but it chose to wait. 

It had waited for that opportunity because it believed that its host would need that power in the future. It also understood that William was not strong enough to consume more than one strand, so it didn't allow him to absorb more.

An hour passed, as Oliver almost crashed to the ground due to exhaustion. The two souls of the dungeon cores floated above William's body and danced like little children. 

The Guardians looked at this scene in happiness as their bodies slowly disappeared into particles of light. They had completed their duty and it was now time for them to disappear from the world. Once the Dungeon Cores had been destroyed, the dungeon monsters that they had birthed would also cease to exist. 

The only proof that the Guardian Beasts had existed were the two Centennial-Grade Cores, and one High-Grade Core that laid on the ground, waiting for their new owner to pick them up. 

-----

Two hours later...

William felt something wet hitting the side of his face. He tried to open his eyes, but they refused to obey his commands. Using all the willpower that he could muster, he forced his eyes open, only to find Ella licking the side of his face in an attempt to wake him up.

"Meeeeeeeh."

William wanted to reply, but just opening his eyes was already a monumental task for him. He stared at his Mama to tell her that he was fine, so she wouldn't have to worry about him. Ella understood what he wanted to convey to her and nodded her head in acknowledgement.

"Oh, you're finally awake?" Oliver's monkey head suddenly appeared in his vision. "Well, it seems that your soul has received significant damage. I'm guessing that right now you are unable to move your body. But, don't worry. It will only take two to three days at most before you regain control of your body. If you can understand my words, blink twice."

William blinked twice to show Oliver that he had understood him. 

The Parrot Monkey nodded its head and continued to talk to William. "I still need to discuss a few things with you, but that will have to wait until you get better. I just wanted to tell you that we succeeded. Don't think about anything. Don't worry about anything. Just rest. That is all you need to do. Leave the rest to me and your Mama Ella."

"Meeeeeh." Ella bleated in agreement. 

William blinked twice before closing his eyes. He was really at his limit and sleep pulled him into her embrace.

When Ella and Oliver heard William's deep breathing, both of them sighed in relief. The other goats had already returned to Lont and only the two of them remained inside the dungeon protecting William.

Soon, the sounds of running footsteps could be heard in the distance. 

"Meeeeeh."

"I know, Miss Ella. For now, I'll hide inside William's shadow and guard him from there."

"Meeeeh."

Oliver's body sank into William's shadow using his Shadow Bind ability. He knew that William would be unable to protect himself at this crucial time, so he decided to become his bodyguard just in case there were malicious people around that would attempt to harm him.

A minute after Oliver merged with William's shadow, Est, Ian, Isaac, Kenneth, Wendy, along with Grent, Andy, and a Cleric, appeared in the dungeon room. When they saw William lying on the ground, Wendy immediately panicked and ran to his side in a hurry.

She was about to lift William's body off the ground when Est hurriedly stopped her.

"Don't move his body!" Est shouted. "He might be injured somewhere. Let the Cleric have a look at him first."

Wendy nodded her head, but she didn't move away from William's body. Instead, she held his hand and looked at the Half-Elf's pale face with an anxious expression. 

Est and Ian didn't say anything about Wendy's actions because they too were worried about William's condition. They waited patiently for the cleric to run a diagnostic spell on William's body so they could see his current situation.

"How is he?" Grent asked. 

"He's suffered from minor internal injuries and is seriously weakened," the Cleric replied. "While his life isn't in immediate danger, he will need a few rejuvenation potions, an elixir, and plenty of rest to fully recover."

Grent and Andy sighed in relief as they exchanged a glance with each other. Although the rejuvenation potions and elixir cost a lot, the academy would shoulder the expenses. It was a small price to pay for the sacrifices that the boy had made in order to ensure that no life was lost during this mission to subjugate the Dungeon of Roaring Quarters.