This is an alternate ending based on Chapter 18 of NT10 in which just as the Magic Gods (and possibly Ollerus) feared, killing one of the pair might cause the other to snap. This one is Touma's half, the beginning of Othinus' half has already been released.
The first bit overlaps quite a lot with NT Chapter 18 (Kamachi's events with my tweaking for better fluidity, changing lines slightly to change the meaning, and adding some lines of thought) in order to make it read better.
However, if Chapter 18 of NT 10 is still fresh in your mind, I've included a marker. Simply use Ctrl + F and search up "*** ***" and start reading from there instead. Keep in mind that the text up until the marker differs between the two halves of this story though.
This will be a two/three-shot just as the other.
Also, a bit of clarification. "Little Match Girl" mentioned several times during New Testament 10 is a short story about a girl with an abusive dad who stays outside during the middle of winter to sell matches, because she's too scared to go home. She lights a few of them and sees things like a Christmas tree, and her grandmother (the only person who was ever kind to her), she keeps lighting more of them because she's afraid the vision of her grandmother will disappear, but eventually freezes to death without realizing it, and her Grandmother's soul leads her to Heaven. The morning after, people walking around the streets find her body and feel bad for her. "A Dog of Flanders" mentioned by Touma in New Testament 10 is a suspiciously similar story, with the female protagonist swapped out for a boy named Nello.
A Certain Alternate Majin: Lost
Chest, gut, face. Her fist struck him again and again. One strike would knock him onto the border of consciousness, only for the next blow to shake him back. She would not allow him to so easily lose consciousness. And during this, the hard sensation on his back had disappeared.
The tree trunk had broken from the impact of those powerful blows passing through his body.
With nothing left to support him, he flew backwards. By now, he was almost nothing but a bloody lump, staining the snowscape as he bounced across it.
"Gah...ah...ha"
He could no longer speak properly. Most of his vision had darkened, but even in that narrow, dark tunnel's exit, he could see the monster known as a "Saint" approaching.
If that was all, he would not have been able to muster up the strength to stand up once more.
However, there was another Saint.
Brunhild.
But that Saint was not attacking him. Because she was targeting Magic God Othinus instead.
"..."
After realizing that much, strength returned to his legs.
His vision shook sporadically, and he had trouble telling up from down. But still, he stood on those shaky legs of his.
But that only angered the Saint known as Silvia all the more.
"Fine then."
He heard the sound of a group of fine threads tearing.
It was the sound of the corners of Silvia's mouth splitting in the shape of a smile.
"I'll disembowel you with my bare hands and show each of your organs to that magic god. You're the treasured partner she abandoned all of Gremlin to be with. Even a magic god won't find it easy to watch as you're vivisected before her eyes.
The dark red mass was still trembling slightly.
He was breathing.
That simple fact brought movement from nearby. An eyepatch wearing girl moved as if crawling along the snow. She moved slowly and sluggishly, but she still made progress toward the bloody mass lying on the snow.
"Hu…man…"
She moved her bloody lips to squeeze out the word.
Her eyes sought him.
He looked like Nello clinging desperately to his last hope. A boy had nothing in this cruel world but a single friend.
"This is why…I told you…nothing good would come of…going with me…"
Othinus...
He had failed many times before. But this time, he would not allow himself to fail.
And so, he reached out with his right hand once more.
But Brunhild remained perfectly dry.
Her expression remained unchanged and she stomped on the magic god's right shoulder. That was all it took to stop her slow progress.
"What will it take to satisfy you?"
"Isn't it obvious? I'll tear out this brat's organs as she watches. I'll make sure he's still alive and moving his mouth the whole time like a fish served alive."
"Stop…"
Othinus was pinned to the snow by the great pressure from above, but she reached out her bloody hand.
No matter what she tried, she could not reach the dark red mass before her.
"You're after me. If you eliminate me, you can end the chaos filling the world. He has nothing to do with it. Just killing me is enough to eliminate your own chaos, so…"
"I don't care." The words spilled from Silvia's mouth and more sticky words continued. "As long as I can kill you, nothing else matters. As long as I can take revenge for that bastard Ollerus, I don't care if I go insane. You don't understand. You really don't. I don't want to go back to normal. If I do, it'll end there. I get the feeling I'll end up forgiving you. But I don't want that. Do you understand? It's not whether I can or not. I don't want to, so I'm choosing not to."
Brunhild had a silent thought when she heard that.
(I need to kill the magic god without waiting for Silvia's instructions.)
Even now, she was not underestimating Othinus's power. She would show no kindness and she would kill when she could kill. She did not want to allow some "fun" now and regret it later.
"Then let's get started," said Brunhild coldly while secretly holding the sword's hilt with tremendous strength.
In the instant Silvia was focused on the boy, she would crush and kill Othinus. She was prepared to battle an enraged Silvia afterwards, but she would make sure to swiftly kill Othinus now. That was her top priority.
"Stop…"
Othinus's dim voice continued and she desperately reached out a hand as if someone had taken a stuffed animal from her.
"Stop! He has nothing to do with my sins! There's no reason to make him bear them! So please!"
Her desperate plea did not reach them.
"Don't worry Othinus. Believe in me," Touma croaked as he tightened his fist once more.
"Yea...I will. You've always come through, haven't you?" Othinus smiled for his sake even as tears streamed down from her eyes.
The two Saints took decisive action and a tremendous wind roared.
"*** ***"
He had promised that he would save her. He had sworn that he wouldn't fail this time.
Brunhild's sword had pierced Magic God Othinus' heart effortlessly.
But he had failed.
Crack.
That may well have been what saved Kamijou Touma's life.
The surprise had stopped Silvia from eviscerating him.
Both Silvia and Brunhild stood still.
The shock at having killed a so-called "Magic God" so easily paralyzed them.
"Othinus, stop playing around hehe." Kamijou Touma refused to believe what lay in front of him.
He tried to deceive himself. "This is a cruel joke even for you, stop it already." He reached out with a bloody hand towards her.
"Othinus...?" But he could no longer fool himself.
Crack.
Without paying any heed to him, Silvia and Brunhild argued.
"Why did you do that?! She didn't suffer enough yet!"
"I have no stomach for senseless cruelty. Magic God Othinus is dead, leave it at that."
"YOU!"
She's...She's gone.
Crack.
Kamijou Touma wrapped his arms around his legs and tensed.
Without the presence of Magic God Othinus, could he really be so sure that what was before his eyes was truly real anymore?
Othinus...
What if the cycle had already started again without him realizing it?
Othinus...
What if this entire trip to Denmark with Othinus had been a sick joke, as she watched from above? Laughing as he believed she had reformed herself.
Othinus...
...No, he refused to believe that much. He refused to believe that the smile that she had shown him was false. Even if everything else was a lie, even if this world had already turned into one massive illusion, he refused to believe that her smile was fake.
Othinus...
What if even without Othinus, the cycle could repeat itself now? Having gained such a possibility due to those endless repetitions. Touma was no expert in magic, and could therefore not answer if such a thing was even possible. So, he feared it all the more.
A low, creaking sound was heard, and from within his despair, he heard a voice. A voice that he had previously ignored.
Hey, why don't we just destroy it all?
No, I have to...that's right, I...there are still people for me to save!
What does it matter? The puny lives of a few million humans is nothing. Let's just go and kill, until both of us are satisfied. That's what you want, isn't it? After all, this just a fake world. They're only toys created for your sake by her. They should be grateful, thanks to you, they regained their lives in this world. And yet, in their arrogance, they killed her. Doesn't that anger you?
Crack.
It does. It angers me a lot.
Then let's go. Let us shower this world in our divine punishment, for taking away the one that was dearest to us.
...but still, I want to protect this world even so.
Kamijou Touma fought hard against the temptation of that voice. He clenched his fists so hard that he bled even more.
He filled his mind with memories of her. Her voice. Her smile. How she looked as she laughed by his side. All to suppress his own desire.
But it was useless.
Dodging Brunhild's sword, Silvia leapt back, only to get her legs tangled by what was left of Magic God Othinus and stumble.
That scene reminded Kamijou Touma of what he had been trying so hard to prevent.
Magic God Othinus being trampled by the world, in the name of "peace".
Something shattered.
"This worthless world has no right to exist."
With renewed resolve he took one step forward on his shaky legs.
When Marian's Dainsleif had been drawn, the requirements for the world's end in each religion could be forcibly called forth. For example, in Greek Mythology the fall of Olympus would beckon the return of the Titans, predecessors of the Gods. In Aztec Mythology the disappearance of the sun would bring forth Ocelot, the man-eater with the head of a crocodile. In Norse, the completion of the bone boat, Naglfar, would herald the beginning of Ragnarok.
This was no different.
That single step was all it took. In accordance with a certain religion, the requirements for the end of the world had been fulfilled.