A Brother's Sorrow (adopted from @Eris345)

Chapter 19

In the end, it's impossible to save the ones you truly love. Humans are mortal, like all organisms are. Or so it seemed.
Monsters were born from the death of other organisms, sifting through time before becoming what we view today as nightmares. They haunt the minds of small children, taking the shape of their darkest fears before brutally murdering their victims within the mindscape.
A nightmare latches onto the mind of someone who is deeply troubled and kills them by draining their prey of any hope of escaping their relentless torture before devouring the weakened soul.
However, there are those who oppose the monsters feeding upon them, lashing out and killing the monster inside their head. Eventually, they will crumble and die inside their own minds, their souls doomed to eternal torment.
Unless they find a way to escape their mind first...but that's impossible...right?
~~~~~~~~~~~~~~
William sank into his bed, finally having lost any hopes of protecting his loved ones. He had disposed of his son's corpse by burying it in the backyard, and now he was both spiritually and physically exhausted. It's over. He's gone. They're all gone. Closing his eyes, he felt himself being whisked away to his torture chamber, but for once, he didn't resist it. There was no reason to fight the inevitable, correct?
Akumu was waiting impatiently, his face having healed somewhat. In fact, he seemed almost...human. "Hey Willi-kins! How's your son?" He then burst out into peals of laughter.
Snarling, William leaped on top of Akumu, pinning him to the...ground? "Shut the fuck up you lousy bastard. Say another word about my family and I'll strangle you to death."
Akumu merely giggled. "You mean your deceased family?"
William let go of the monster, slumping to his knees. "No...they're not gone. They aren't."
"Just give up already! You're more useful to the world dead! Nobody loves you. You've hurt so many people. Why won't you just die?" Akumu whispered seductively, breathing into the man's ear.
William closed his eyes, his resolve unwavering. "No."
Akumu staggered back, clutching his chest as if he was in pain. "W-what?"
"I said no," William shouted, his voice stronger than before. "I will save those who remain, and I'll ensure that the sacrifices I made aren't in vain!"
"You have no right to speak of sacrifice, Afton," Akumu hissed, his eyes glowing a bright red. "I am the only one who's making the sacrifices here!"
William rose to his feet, his determination taking physical form. A knife appeared in his hand, it's tip sharp enough to cut through titanium like butter. "I won't give up just because the world is against me! I will fight back and reclaim my mind!"
At this, Akumu burst into laughter once more, rolling on the ground. "You honestly think you have the upper hand here? I WILL ENSURE THAT I SUCCEED!"
William felt a heavy weight suddenly appear upon his back, forcing him onto his hands and knees. After struggling for a few seconds, he flopped onto his stomach. He looked up at Akumu, who had appeared standing before him, with pure hatred burning in his irises.
"My reincarnation will begin, Willi-kins," Akumu said, his red eyes softening and taking on a human-like appearance. "Thank you for sacrificing everything for my return."
"N-no...this is my body..." William whispered, his eyes welling with tears.
"Didn't you say you'd do anything to see me return to life, William?" Akumu whispered, running his hand through William's hair in a melancholy manner. "You didn't need to kill those innocent children. All I needed...was your body." Smiling weakly, he turned and disappeared, finally returning to the real world.
William, meanwhile, was left to rot inside his own mind, patiently awaiting the day he could take back his body. Sadly, he never had the best of luck. And so, he would be left to rot inside his own head for decades.
(You did it. You saved him. You brought him back. I told you that you guys had the power to change fate, and here is the consequence of your actions. Congratulations.)