Hi! I decided to do an Undertale/PJO crossover, as it seemed like an intriguing way of crossing worlds. PJO with its monster-killing ways and Undertale with its Pacifist/neutral routes. Includes genocide flashbacks from time to time, so I recommend playing Undertale before reading this. But read on and enjoy!

Muffet POV

"My head hurts." Muffet groaned to no one in particular. They had been on the surface for around two months, though she still occasionally got headaches from the sun. Well, maybe that wasn't entirely true. It could also have to do with Mettaton, who had been begging for her permission to do a review on her bakery.

"Muffet," Queen Toriel called, the door ringing out its greeting, "You needed some medicine?" Muffet nodded, one of her six hands reaching over and taking a five dollar bill from the cash register.

"I don't need to be paid for this, Muffet." Toriel protested. "I wouldn't hear of it, dearie, you've helped me set up shop the past couple weeks, so you deserve more than this, but you wouldn't accept it, would you." Muffet replied.

Toriel knew better than to argue with Muffet's offer, so she graciously accepted the money, leaving the medicine on the counter. Muffet measured how much she'd need, and quickly swallowed it. Just in time, because Mettaton burst through the doors, Napstablook and Burgerpants with him. "Muffet, we-"

"Go away, robot! I'm not letting you review this place. You'll just tear it apart." She glared at him.

"Darling, it's not that, we're supposed to tell you about the humans who've arrived!" He exclaimed, sounding somewhat nervous.

"Humans?" Muffet's interest was piqued. "Like Frisk?" "Yeah…" Blooky replied. "Let's go meet them, shall we?"

Percy POV

"Get up, Seaweed Brain!" Annabeth called into the Poseidon cabin. He groaned and rolled out of bed. "Do you want to hear what Rachel's vision was about or not?" He saw her stick her hand into the fountain in the center of the cabin and cup some water in it.

She ran over and splashed him. "I'm going to get you for that, Wise Girl!" He laughed, catching her wrist and pulling her down to the ground with him. They lay there for a moment, laughing.

"Okay, Seaweed Brain, you need to get ready for the day." She reached over and tapped him on the nose. "Yeah. I wonder-" he began. "No wondering until you get dressed!" Annabeth pulled herself to her feet and walked to the door. "Seeya later, Seaweed Brain."

Percy grabbed an orange Camp Half-Blood tee and some cut-off jeans and threw them on. He pulled on some tennis shoes and ran out the door, heading for the big house.

"I saw monsters being released by a child. A non-magical human." Rachel specified. "They had the aura of at least two people though. It was concerning. They managed to destroy a barrier that had stood for over 400 years. I have reason to believe that the Olympians want us to find this child."

"We need a prophecy to do this quest, though." Nico murmured, looking through the paintings Rachel had made early that morning.

"I knew you'd say something like that. That's why I saved this poem for last." Rachel took a deep breath.

"Monsters arise from the underground,

A human with power that needs to be found.

Heroes stand strong, follow the war,

Lose to the soul, and might of Asgore.

Bring the human to the Olympian king,

Wait for the monsters, when freedom will ring.

As 9 heroes unite, join in the fight,

And bring back the dying red light."

Rachel finished, looking around the room for any questions. Percy slowly raised his hand. "Who's all going?"

"Well, the Seven are here, but when I heard the prophecy, I noticed the 9 part. Does this mean two more demigods?" Chiron pointed out.

"It didn't say all of the heroes would be demigods, Chiron. I don't want to risk more lives." Mr. D said. "We'll send Nico along with everyone else. From what I've seen from Rachel's paintings, there's a skeleton dude! Hazel can't necessarily manipulate the dead, so Nico is opportune for that role."

"Genius." Chiron stated, "Pack your necessary supplies for the trip. From the description Rachel gave us, their camp is on the northern borders of Pennsylvania and Ohio."

"Annabeth." Nico called. Percy walked over with Annabeth and Nico showed them one of Rachel's paintings. It was a girl with pale violet skin, five eyes, six arms, and surrounded by spiders. Annabeth stared in horror. "Kill it with fire." She whispered. All the more reason to vanquish/slay these monsters.

Hazel POV

Hazel looked around the clearing. "Are we certain-" she was cut off by a loud "Shh!" from Nico. Hazel watched silently as a group of monsters rounded the corner.

"Well, punk, I didn't think you had it in you, but you're ready to become a royal guard!" A blue fish monster with red hair and an eyepatch was saying brightly, slapping a tall skeleton on the back with her armored hand.

"ME? WOWIE! I'M FINALLY GOING TO BE A PART OF THE ROYAL GUARD! WHEN WE GET BACK, I'M GOING TO TELL SANS!" The skeleton exclaimed excitedly.

"Ah, c'mere, you!" The fish monster grabbed the skeleton and forced him to lean over. She then gave him what appeared to be a hard noogie. "ACK! PLEASE DON'T- NOOGIE THE SKELETON!" He shouted.

The fish monster rolled her eyes. Nico seemed tense. "What is it, Nico?" Hazel asked. He jumped. "Oh, sorry. I was just- I can't feel the aura of death around the skeleton. In other words, I can't control it."

The others exchanged worried glances. "I'm sure we will be able to defeat these monsters." Hazel murmured, patting her half-brother's shoulder with a smile.

"Yeah, Neeks." Leo said, "Everything's gonna be just peachy! We'll all get back to camp safely, and we'll sit around the fire eating pie and ice cream!"

Everyone "Shh-ed!" Leo collectively.

"What was that?" The fish monster said, her voice serious and stern. No more joking was apparent.

"WHAT WAS WHAT, UNDYNE? DID YOU HEAR SOMETHING?" the skeleton asked. "Nah. Let's head back now, Papyrus." Undyne said, turning back down the road. Papyrus ran on ahead, but Undyne turned around, giving the surrounding area a long inspection with her lone eye before dismissing it and leaving.

"Whew!" Piper breathed, breaking the suspenseful silence. "You know, I really hope that we don't end up staying in this tree all night."

"We probably should find a place to sleep." Jason shrugged. Hazel reached into her bag, pulling out a gift she had gotten from Reyna before she had left for Camp Half-Blood. "I have a feeling you'll need it." Reyna had said.

Hazel pulled it out of its thin case and tossed it to the ground, climbing down after it. "What the-" Percy stopped short. The fabric was becoming a small, camouflaged tent, though it didn't look large enough to hold 8 people.

Hazel stepped inside. "Whoa." she whispered. The tent was huge on the inside! It had a shelf holding sleeping bags, 10, to be exact, and had necessary supplies in the cupboards lining the back wall.

"I'm not sleeping next to the cupboards!" Leo called. "I'm not going to be the next Flat Stanley!" Hazel rolled her eyes.

"Where'd you get this?" Frank asked. "I don't know, but I want one." Leo cut in before Hazel could reply.

"Reyna gave it to me." Hazel said before Leo could butt in again. "Aw man! There goes my chances of getting one!" Leo waved into the air. Most likely to his sanity.

"We should go to bed before it gets dark. We'll want to get up early and hide from any patrols." Percy zipped up the entrance. Soon, seven of the demigods lay sleeping. Except Hazel.

She lay in her sleeping bag and watched out of the hidden window as the stars glided by. Her thoughts were plagued by how the monsters had interacted with each other.

They had been so… human, in their movements, their voices, how they acted. The skeleton, Papyrus, wasn't a corpse brought to life. He was a living thing. But… How did that work? She didn't know if she would be able to kill these monsters if it came down to it.

She let her mind rest, drifting to the traveling, the pranks Leo had played, the information Annabeth had given, Frank almost driving the car off of a cliff… yes, it was good to reflect… she felt consciousness being tugged away from her, and her heavy eyelids slowly closed, trapping her in a world of dreams.

Well, that was an experience. I'll put up more soon, but if I made an error or fault in the lore, feel free to leave a review! (You can leave a review if you liked it as well, if you'd like.)