I just realised considering Eren's age, Grisha should be dead by now because of the 13 years curse. I am changing that, there will be a curse, figures that I should mention that. That is all.

Disclaimer: I do not own Attack on Titan. All characters belong to Hajime Isayama.

Year 844 1 year before the breach

While the walls are one form of protections of the horrors beyond, the earth provides another with its solid ground and hard rocks. Deep underground lay a giant cavern, so vast only few pillars holding it from collapsing. A city, part of an abandoned expansion project turned into a penitentiary, every criminals unlucky enough to find themselves getting caught will be stripped of their citizenship and be left to die down here. Children born here had never seen sunlight nor breathe the fresh air, they knew it requires a strong will to survive down here.

Eren doesn't remember much before he passed out, he remembered running then stopping after that a firm grip on his neck choking him, there was a flash of green before darkness overcame him. He woke up in the middle of a street, confused and alone, he dashed to a nearby building making him less exposed as he tried to remember. He felt like his heart stopped for a moment, as he looked around, finally remembering it all. First priority, survive, he walked down the street with the best scared and confused face he could muster. He only just past the first street when someone was already following him, running is not an option, they are not going to be the only one after him. His only weapons were sticks and stones, he just have to get the jump on them.

Lotte was living the good life, he grew up in this shithole of a dump then managed to get lucky enough to land himself with a job at a big slave market. Not the biggest but enough for him to be well off, the slaves are a bonus too. Currently there aren't enough slaves to sell, so that's why he's on the streets looking for fresh, healthy, child. He was lucky, there in the middle of the street, a boy, looks like he either fell or got tossed here recently, there aren't many aboveground kids, if there are they sell for a lot. Many sick fucks love to get their hands on them, turning pure, innocent children into a willing dirty little sex slave. Putting on a concerned expression, he followed the boy until he could lure him into an alleyway, he turned straight into one, much easier for him.

"Hey kid, you looked a little lost. Do need help?" usually this won't work with underground kids but this one is new from the surface, shouldn't be too much trouble, they lived a simple life after all. He walked further in when he saw no sign of the boy, all of a sudden a rock came flying towards him, hitting him in the face. Hissing from the pain, he just barely miss a stick coming at him, being held by the boy, he caught the stick with his hand, he moved too fast. The makeshift spear broke off from his arm, one being held by him, the other end by the boy closing in on his throat. Choking from it, he took out his knife, being blocked by his other hand still gripping the broken stick, he intended to force the kid to back off when all of a sudden he was shove, a sharp sting on his stomach, losing his grip on the knife the boy, who used his body to shove him, quickly grab the knife and jump back, making the sting on his stomach much more painful.

Eren knew he only had one chance in this, shoving his hand into his pocket he pulled out a stone, it was as big as his hand but he can hold it firmly enough for a steady throw. He also took out a stick, thick enough for him to use as a makeshift spear, considering this man has lived here longer than him, he'll expect an attack. So he broke off the end of it, short enough for spare, long enough for the man's arm to took hold. After the counter ambush he just stood there, watching as the man held his stomach in a fruitless attempt to stave off death. "Shit kid" he wheezed out "Y-you're good" there wasn't even hate there just acknowledgment, as the man finally took his last breath, he checked the body for foods, drinks and information. He was the first of many that surely to come, and he needed to be prepared.

After few months, Eren made his first new friend in a form of mice, the area he was staying in had a few of them, scurrying to and fro. He managed to train some of them, a few for scouting, a few more for carrying small objects, while the rest warn him if there's danger. Rats were a choice but some desperate people would eat them, mice are to small to satiate their hunger so people don't bother too much. They're surprisingly good allies, he managed to train one to cut ropes and pick locks, he called this one Caeg. Currently he was sitting on top of a building looking over a market, finally after constant searching, he found the slave market.

It was nearing the end of the year, Louis Walter was perusing over the documents of the newest batch that'll be joining in next new year. The list increased significantly half a year ago when one of the largest slave market was destroyed and the other two subsequently, it all thanks to someone who was called by the poeple of the underground, as wolf. As he was halfway thru the paperwork, Artemas came in looking extremely giddy, "Am I interrupting, sir?" he asked. Shaking his head "Not at all, now what has got you so excited?" Louis asked as Artemas sat down on the chair opposite to him, a file in hand. "Do you remember the mission you gave me?" he asked "It was more of a request, but I do" Louis answered, he asked Artemas to looked for Wolf. They will make a fine addition to safeguard the Walls from them destroying it, Artemas must had found them then. "Well I found him you will not believe it, its them sir, it was a chance meeting, but I never forget those eyes. Sir, I'm certain its them" he said as he pushed the file, there is a description the person. Louis swore his heart stopped when he saw those golden eyes, 'How'.

In the underground city, where criminals lived and the strongest and the most skilful can survive, was a surprisingly quiet place, the silence was broken by the sound of the omni-directional manoeuvre gear, gas releasing, wires flying, the thud and chunk of grappling wires finding their mark. The ODM gear was a revolutionary personnel gear design to combat the titans, but with a bit of tweaking and training, it is the best fighting gear to prevent the horrors outside from getting in the Walls. Louis and few other soldier were flying near the roof of the cavern searching for the Yeager boy. Yeager, a family he thought would ever still be alive, they were a family used to be feared for their unshakable will and crafty nature, same as the Ackermans for their loyalty and prowess as a soldier.

To find him they need to look from above and they only have one chance of meeting him, once the kid knows of this ODM gears he will find a way to counter it. Reports said the kid's territory is here, they just have to wait. It didn't take long as the kid was exiting a market walking in the middle of the street with a face that radiates full innocence, Louis would be impressed if he wasn't concerned by the meaning of it. When he went inside what to be believe was his house, Louis and his men immediately went down to it, few guarding his back while the rest guard the perimeter. He took a deep breath and knocked.

Eren was sharpening his newly acquired knives when he heard a knock, looking at his mice they squeak fighter and confusion, not knowing what they want he told the mice to look around, while he answer the door. After making sure Caeg was hidden within him he opened the door, finding a soldier from the ground above, adding to his confusion was the insignia, which is a crossed sword overlapping a shield with a wolf also overlapping them. The soldier looked relieved "Mr. Yeager how good it is to see you" Eren's eyes became sharp looking straight at the soldier "We would like to make a proposal to you. There are horrors outside the walls that is bigger than titans, we need people like you to help defend it" he looked around finding his mice at some hiding spot, meaning there's more than just the soldier in front of him. He was about to closed the door the soldier talked again, he looked desperate "Please Mr. Yeager, would you not fight for humanity's survival? There's more than just titans out there" Eren eyes became unfocused, remembering something, a promise he made with his father.

"Son, I don't care if you became a soldier or the devil itself. Promise me this one thing"

"Sure dad, what is it?" there was a light of energy coming from his father staying in between them.

"Promise me you will fight for humanity's survival"

"I promise, whether good or bad I'll fight" a light coming from him met with his father's before binding together.

"I'll join" Louis was shocked by the answer, he didn't think the words were that convincing but the kid looked like he remembered something before agreeing, he nodded. "My friends will come with me, and you'll tell me how much you know about me" well the demand wasn't that hard to comply, there a lot more kids with more wilder demands. "Sure kid, you're friend can join although, I do require a first name for paperwork" the kid narrowed his eyes before whistling, at first he thought it was a dog, but mice started running to him. 'Well, they are trained, hopefully there won't be too much chaos' he thought, the kid cooed and petted them before saying "Eren, my name is Eren"

"Well Eren Yeager, welcome to the Arnoux regiment"

Unfortunately, English is not my first language if there is some errors please comment on it I will fix it if there is.

I know where the story will go but I find it hard to write it down. There will be slow updates unfortunately.

Hope all of you stay safe.