So I ran across this image that showed Misty being killed by a Muk and I thought, why not give it a back story? Enjoy.
"So if we continue south, we should hit Lavender Town soon." Brock reported, "This feels just like old times huh?"
"Yep, and you still owe me a new bike, Ash" Misty joked.
"Still with that?" Ash laughed before bumping into Brock, "Whoa, what's wrong Brock?"
"Umm...that's strange." Brock replied as he looked at his map then straight ahead.
"Are we already there?" Misty asked as she saw a small town ahead.
"No." Brock replied with confusion, "The map clearly states that we are still about an hour or two away...but then...what is this town?" Straight ahead was a town next to a forest, old yet it somehow looked recently built.
"Maybe it was built while we were gone." Ash suggested.
"Maybe, but I would've heard about it." Misty replied, "I was here the entire time you two left."
"Let's ask around." Brock continued, "Maybe someone can shed some light on why they aren't on the map."
The three moved onward, into the town. At first, the town seemed deserted, but soon more and more people came around the corner as if they were all in the back of town for a gathering. One by one they resumed their daily lives yet they all seemed...depressed.
"You guys notice their faces?" Misty asked. Brock and Ash nodded as they looked around the town. Misty was about to turn to look around, when an old lady did it for her.
"YOUUUU! BEWARE OF THE SLUDGE! LEAVE THIS PLACE AT ONCE! LEAVE!" the old lady screamed as Misty tried to pry her off. Some of the townspeople came up and pulled the old woman off, her cries of warning tuning into mutters as she was lead away.
"Sorry, she hasn't been herself lately." one of them apologized, "Not since her husband died last year."
"Oh, I'm so sorry." Misty replied.
"If you don't mind me asking, why does everyone look...depressed?" Brock asked.
"Oh, today is such a sad day." the townsman replied sadly, "this is the day that most families lose their loved ones, both young and old."
"What? How?" Ash asked.
"There have been rumors of a Pokémon who takes random visitors and kills them, always on this day." the townsman replied.
"You mind sharing the story?" Brock asked.
"The story goes that a trainer came across this town, deserted and unknown, yet he was sure that the town didn't exist the day before. The trainer was accompanied by his only Pokémon, a Muk. He decided to spend the night, seeing as how homes were already build, furnished, and had food in storage. The first night, everything was fine, but then the next morning, Muk didn't want to leave, so the trainer decided to say the week. People arrived that day and decided to rest as well, but late that night one of them went missing. The body was found later covered in purple gunk. The young trainer disappeared after trying to prove his Pokémon's innocence on the third day. One by one, travelers who happened upon the town were found dead. If it was a group, one of them would die, and the rest would become part of the town. It is said that those who are targeted by Muk, disappear until they are found the next day."
"But, that's not possible." Ash replied, "Pokémon don't kill humans, they only attack if they're in trouble."
"That is what they all said." the townsman replied before walking away only to be stopped by Brock.
"Wait, you said it takes visitors." Brock stated, "How is it that these people lost their loved ones?"
"We were all travelers once." the townsman replied and began to walk away, muttering audibly, "Then our travel ended here."
The three watched silently as the townsman left. "That's...a pretty good horror story I guess." Brock commented and Ash nodded.
Misty, still confused at the explanation, looked around to see the townspeople going about their own business when something caught her eye.
"Ash, do you see that?" Misty asked while pointing in the direction of the spotted object.
"What?" Ash asked as he took a close look, "Misty, I don't see anything."
"I could've sworn I saw something purple..." Misty replied.
"I don't know about you, but we should get out of here," Brock commented as he led, "its getting late and Lavender Town is about another couple of hours away."
"Brock, what are you talking about?" Misty asked, "Its mid-day." Brock continued walking.
"Yeah, you're right." Ash replied and followed Brock.
"Wha-? Hey wait for me!" Misty shouted and ran after them. Just before they exited town, the old lady from earlier came up to them.
"Wait, you young travelers must be tired and hungry, why don't you spend the night here?" she asked.
"Didn't you just warn us to leave?" Misty asked.
"We really don't have anywhere to stay here." Brock replied.
"You can rest at my home for tonight." the old lady replied.
"Alright then, thank you." Brock replied, "We'll rest tonight an- wait where's Misty?" Brock looked all around him.
"What are you blind!?" Misty shouted, "I'm right in front of you!"
"Hey, you're right." Ash commented, "Where did she go?"
"You too Ash!?" Misty asked.
"My, I hope your friend returns soon, or the Muk might get her." the old lady said jokingly with a laugh.
"Muk?" Brock asked.
"Oh, it's just a silly scary rumor." the old lady replied, "Nothing to worry about dear."
"What's wrong with you? A man just finished telling us the story!" Misty shouted.
"I'm sure she'll turn up soon." Brock commented, "Probably wanted to look around when you asked us to stay."
"...oooh I get it." Misty laughed, "You're trying to scare me. Well it isn't working so cut it out."
"We should get to sleep then." Ash commented, "If I learned anything, it's that I don't get enough sleep because you wake us up early."
"Sure," Brock replied the turned to the old lady, "If you see Misty, will you let her know we'll be at your place?"
"Of course dear." the old lady replied as they left, leaving Misty alone.
'Well if you want to scare me that bad, how about I scare you by not coming out till tomorrow?' Misty thought to herself before feeling something slimy hit her leg. She looked down to see a purplish blob of gunk on her leg, "What the-? Oh, real mature guys!" she shouted before walking off to the forest. "Try and scare me will you?" Misty mumbled as she went deeper and deeper into the forest.
Misty stopped at a clearing, odd as it may be, but it wasn't the clearing that caught her attention, "What the hell? When did it become night time?" she asked herself before being spooked by the sound of rustling bushes. "H-hello?" Misty called out, but only a quiet bubbling sound could be heard. She felt like running back, but one thing prevented running, "M-my leg is...numb!?" she thought out loud as a blob of purple sludge hit her on the shoulder, but the numbing effect was quicker.
Misty tuned and fled as quickly as she could, dragging her numb leg along as much as she could. "There's the town!" she said to herself before another blob of sludge hit her other leg, numbing it and causing her to fall. Misty looked back to see a Muk approaching slowly. She quickly dragged herself with her working arm toward the edge of town. As soon as she entered the town, Muk stopped at the edge of the woods. It stared at her for a few minutes before disappearing into the shadows.
Misty breathed a sigh of relief but quickly became confused again. "Wha-? Its daytime!?" As soon as she finished her sentence, Muk appeared in front of her and fell upon her, covering her up to her waist. "NOO! STOP!" Misty shouted as she tried to drag herself away. Misty began to panic and searched frantically for anyone who could help her, hope came around the corner.
"ASH! HELP ME! HURRY!" she shouted as she stretched out her hand to him, but Ash just stared at her.
"Why would I do that?" he asked in a monotone voice, "I don't know you."
"ASH! WHAT ARE YOU TALKING ABOUT!? HELP ME!" Misty shouted. Muk was up to her chest already, her numb arm taken along with it.
"What's going on?" a voice asked as the owner came around the corner.
"BROCK! HELP!" Misty shouted as she continued her attempt at dragging herself free, but muck was up to her neck.
"Who are you?" Brock asked.
"Not you too! It's me! Misty!" she replied.
"You're not Misty." Ash replied in monotone, "Misty is dead."
"Why won't you help me!?" Misty cried, tears began to flow down her cheeks as Muk reached her mouth. Its sludge began to make its way into her mouth and down her throat, causing her to gag and cough in an attempt to keep it out, but the sludge began to force its way down her throat, into her stomach and lungs. Misty frantically clawed the ground as her vision blurred and disappeared under Muk along with her head. Her hand continued to claw at the ground in failed attempts, weakening with each passing second.
Ash and Brock watched as Misty's hand made one final slight twitch, then relax as Muk took it. Misty felt her once good friends stare at her as the embrace of death consume her.