Hey guys, it's the Reborn Crystal here. This is my first story, A Time-traveler's Determination. It's a PMD X Undertale crossover. Anyways, here's the full summary.

Summary: Takes place two years Darkrai's defeat. It was supposed to a normal solo mission. Just check out strange activity in some ruins and report back any findings. Sadly for Autumn, a former human from a blackened future and Co-leader of Team Dreamstar, things are never simple or easy. Now in an unfamiliar world, she falls into a place known as 'The Underground', where monsters unlike Pokémon roam, seeking to take her soul. Autumn is determined to escape the Underground to see her best friend, Louis, once more. Will she befriend the monsters and escape? Will she perish trying? Or will she take a dark path and slaughter anything in her way to escape?

I DON'T OWN POKEMON OR UNDERTALE. POKEMON IS OWNED BY NINTENDO AND UNDERTALE IS OWNED BY TOBY FOX.

Enjoy~

Prologue: Forgotten Ruins

Sunlight shined through the mouth of Sharpedo Bluff, hitting a certain human-turned-Ninetales' eyes. Her eyelids fluttered as she was aroused from sleep. Autumn groaned as she opened her eyes.

"Morning already?" she yawned, stretching her legs as she got out of her hay bed. She looked over to the bed next to her. "Better wake up, Louis."

In the bed next to her was a Luxray. This was her best friend, Louis. She couldn't believe that's it's only been three years since her and Louis met that fateful day on that beach and form their own exploration team, Team Dreamstar. It seem like so much longer. Then again, she guessed it was natural for her to feel that way. After all, she was an amnesic. Even though she knew that she was from a ruined future, Autumn still can't recall her life because that day she woke up on the beach.

"Hey Louis," Autumn said as she shook her friend awake. "It's morning. Time to get up."

Louis groaned as he slowly got up. "Five more minutes" he said, before slumping back down.

Autumn rolled her eyes. "Come on, Louis, it's time to get up. We gotta check out those check out those ruins today, remember?"

Recently, there had been some strange activity going on some ruins of an abandoned town called New Sun Town. A few months ago, some Pokémon who visited the ruin of the deserted town suddenly disappeared. Chief Magnezone and his Deputies Magnemites investigated and found no trace of the missing Pokémon or had any clue of what happened to them. The exploration teams that investigated turned up empty handed too. The case ran as cold as ice. However, about two weeks ago, it happened again, only this time it was an exploration team that went missing. Gold ranked Exploration Team Enigma had been one of the team investigating the disappearances. The team consisted of a Delphox, a Mismagius, and an Absol. They were last seen not so far from the ruins. Last week, Louis and Autumn decided to start investigating themselves.

Louis then slowly got up for real. His face seemed rather pale. "Yeah, you're right."

Autumn saw how pale he looked. "Woah, are you feeling alright, Louis?" she asked, the worry on her face what as plain as day.

"Truthfully, I don't feel so good," he admit groggily, "My stomach is tossing and turning. I feel like I'm going to throw up any second now."

"Maybe we should check out the ruins some other time," she said." You're obviously sick and in no condition to be outside, yet alone exploring."

"Just go without me," he mumbled. "We know that any information by investigating can help find those Pokémon. It's best not to let me being sick stop us from help them in any way we can. Besides, we've both been on solo missions before. It should be that hard."

She knew he was right. That every day wasted would decrease the chance of ever finding those missing Pokémon. She knew she's been on solo mission before, going to places like Oblivion Forest and Destiny Tower, and that Louis also been on his fair share on solo missions to places such as Treacherous Water and Zero Isle Center.

"Well, if you're sure," she said, still concerned over Louis, "I'll ask Aunt Kangaskhan if she can check on you later. You should go get some rest. I'll go and investigate the ruins."

Louis slumped back down to his bed of hay. "Okay" he murmured.

Autumn smiled as put the treasure bag around her neck and proceed to the entrance to leave.

"Autumn," Louis murmured.

"Yes," Autumn said as she turned around to face her best friend.

"Be careful out there, okay," he said.

Autumn flashed a teasing smile "And since when am I not?"

"I can think of a few times," he joked.

Autumn laughed. "Fair enough. Don't worry, I will. I'll see you later."

"See ya later, Autumn," he said as Autumn exited Sharpedo Bluff.

After getting the proper supplies and asking Kangaskhan to check on Louis later, Autumn proceeded head to the crossroads. She couldn't believe how peaceful it has been for the most part since Darkrai's defeat two years ago. During those two years, Team Dreamstar finally reached Guildmaster rank and her and Louis were finally able to evolve. Though she knew that here will always been Pokémon in need and outlaws causing havoc, crime has gotten down a lot and there were less chaos overall. In fact, this whole New Sun Town incident was the most chaotic thing that happened in the last two years.

When Autumn reached the crossroads, she pulled out her Wondermap from her bag.

"Let's see," She was trying to locate New Sun Town on her map. "From what I know about New Sun Town, it was an abandoned town east of the Northern Desert, soo… ah! Here we are."

She put the Wondermap away and proceed to head west.

New Sun Town was said to be once a small town that was establish so travelers heading to or from Northern Desert could rest. However, about 100 years ago, the residents of the town suddenly vanished without a trace and no one has lived there since. Some believe that the residents just abandoned the town one day due to the excessive heat and constant dust storms, while others believe that it was something much darker and sinister that caused their disappearance.

Autumn walked through the town, looking at the abandoned stone brick buildings that were worn by weathering and lack of care, trying to find any sort of clue to the recent disappearances.

She went inside one of the buildings. It seemed to be a house. The stone floor was completely covered in dust and bits of hay poking through the dirt. Not finding anything of importance, Autumn proceeded to the next room.

The next room appeared to be a study. Bit of old paper too worn to read scattered the dust covered floor. The remains of an old desk laid collapsed in the back of the room. At first glance, nothing seemed out of the ordinary, but as Autumn moved noticed that the dust surrounding the broken desk was displaced, some parts revealing the stone floor.

'Someone must have moved it recently' she thought. Autumn then pushed the remains of the desk out of the way. Beneath the remains was a trapdoor of sorts, possibly leading to a basement or cellar.

'Well, might as well check it out,' she thought as pulled open the door and proceeded to climb down the ladder that was placed there. At the ladder was a room with stone floor and walls and large circle painted onto the floor.

'What is this place?' she thought, 'Some ceremony place for a cult that uses Pokémon sacrifices for religious purposes? I hope not.'

On the eastern wall, she saw some very familiar ancient language.

'Unown? What's this going there?' she thought. After the Temporal Crisis and her return, Autumn took it upon herself to learn how to read the Unown language. She knew that the language hasn't really been used regularly in hundreds of years. She doubted that the previous occupants used the ancient language in their everyday life. She began to decipher it in her head and what she translated just confused her.

START LOAD SAVE RESET DETERMINATION.

"What?" she said out loud, "This doesn't make any sense!"

Shaking her head, she headed to check out the western wall, but what Autumn saw only made her even confused. On the wall were strange symbols. While she's didn't know how to decode footprint runes, she had seen Louis translate them, so she could tell that these weren't footprint runes. This code was unlike, to her memory, anything she had ever seen before. It consisted of different symbols such as snowflakes, human hand signs, flags, etc.

As she continued to stare at the strange code, trying to wrap her head around it, Autumn suddenly felt like someone was watching. She quickly turned around, only to find no one there. Most people who assume that it was just their imagination, but with everything she had been through, Autumn wasn't as easily fooled.

"Who's there?! Show yourself!" Autumn shouted as she walked to the center of the room. However, when she reached the center of the circle, it started glowing with black energy.

"Wha-"Autumn barely had time to register her shock as she suddenly felt herself falling.

The last thing Autumn knew before blacking out was a strange sensation running throughout her body.

Thanks for reading. Please fav, follow, and post your thoughts of this story so far in the review.

Yes, in this story, Autumn (my PMD explorers hero) replaces Frisk.

Anyways, this Reborn Crystal signing off.