It was a new moon night. Mettaton and his sister, Chitron, were outside enjoying the incredible view. However, the enjoyment didn't last long. The duo saw a shadow of a creature fly above the ground.
This was no ordinary creature. It was huge with dragon-like wings. Chitron was so fascinated to see a real dragon that she wanted a picture. Mettaton then pulled out his cellphone and took a picture of it. However, the flash got it's attention.
The dragon began to dive to the ground while locked onto Chitron. As he passed, he snatched the little girl in his hand. It turned out the creature wasn't a dragon.
Mettaton tried to keep up with the beast and his little sister, but failed miserably. Chitron struggled within the monster's grip, and he got sick of it. The monster then revealed it's full face with a third eye on his forehead. Seeing the eye caused Chitron to faint.
When she woke up, she was in a cage with another little girl. When she looked around, the whole place was packed with children trapped in cages. The beast came in the room, which turned out to resemble Mettaton, but bigger. The emblem on his belt was a red "X", and his black hair was highlighted with red and yellow. He wore a red cape and had dragon wings sprouting from his back. His eyes were yellow, 2 hidden behind his hair, and his fangs and claws were like spears. And his name was Vortex.
Chi was nervous. Her palms were sweating with fear. Her heart was pounding. Her stomach was in knots. Her eyes welled up with tears. She hugged her cellmate and wouldn't let go. But, it turned out the other kids were in cages months before her, and some were never heard from again. But nobody knew what happened. This was the reason that there were missing child posters all over the city, and Chitron recognized most of them, including her cellmate.
Vortex would not take his eyes off of anyone for hours, and his stare was intimidating. Eventually, he got tired and collapsed on the floor. This was a chance for a jailbreak. Chitron had a spare bobby pin in her hair, and she used it as a key to unlock the cage. But then, something unexpected happened. The rope that was supporting the cage ripped and the cage broke. The noise woke up Vortex. Chi then dashed to the nearest hiding place, but her cellmate didn't make it.
Vortex grasped the girl with his mighty claws. She struggled. The terrible beast revealed his third eye, causing her to pass out. He opened his maw and swallowed the child in one gulp. Nobody else saw it except for Chitron. She was horrified by what she saw.
Chi frantically unlocked each and every single cage, releasing them. But as they turned to leave, Vortex stood in their way. Then he fainted and swallowed every last child, including Chitron. They all woke up in his stomach, and Chi was being hugged by all the frightened kids. She had lost all hope.
Meanwhile, Mettaton was in search of his sister when he came across an abandoned cabin with scratch marks and engraved X's all over. It was sure that Vortex did all that, and it was where he was, anyway. Mettaton kicked down the door. Literally. Inside was Vortex with a full belly. The first thing he did was shoot at his belt, but no weakness. Vortex laughed and said that someone as puny as Mettaton would never beat him. But MTT wasn't paying attention to what he had to say. However, he was rather focused on the glow in his mouth. As soon as Vortex got a grip of Mettaton, he went straight to the uvula and started kicking and shooting at it. This made Vortex hack up all the lost children, except for Chitron. She found one more girl in a ripped outgrown onesie with the same marking as Vortex.
The two girls started up the gullet, and as they exited out the mouth, MTT decided to finish Vortex, so he started charging his laser. But the girl stopped him. She said to not hurt her big brother. That's when Mettaton realised that she and Vortex had the same emblem. They were brother and sister after all. Then the girl insisted that she'd take good care of her big brother. That's when Vortex explained his backstory...
When he and his sister were babies, he accidentally ate his own sibling. She tasted delicious, but he felt guilty about what he had done. Then, to get out his anger, he started preying on other children. The first attack was at a summer camp which the cabin he currently lodges in had every last children never heard from again.
But now that his sister is alright, he won't go on anymore rampages. He now feels accompanied by someone who loves him.
Moral: Don't judge a book by its cover.