One night, Chara and Asriel were having a sleepover together. Or, rather, they had been allowed by Toriel to stay up late with the promise of no school the next day and were free to do as they wished that night. Neither child had ever had a proper sleepover, but Chara knew at least something about how human children typically enjoyed these types of nights.

At that moment, the two children were sitting underneath the cover of Asriel's bed, with Chara holding a flashlight over their face. Asriel had a bowl of popcorn in his lap and was eating some as Chara told a scary story. The young ghost monster was shaking slightly as his sibling spun a creepy story, with the flashlight illuminating their face.

"...and then, the child looked into the abyss, hoping to find someone to save them," Chara said, turning their face away from Asriel.

Chara went silent for a moment and Asriel asked cautiously, "C-chara?" His paws were shaking and he was doing his best to be brave.

Chara then spun around quickly, their eyes completely blacked out. Their mouth appeared to be dripping with a black liquid as they yelled out, "But nobody came!"

Asriel screamed out and jumped, spilling popcorn all over the bed. Chara was doing an evil laugh as Asriel hid his face. The human's face returned to normal and they began to giggle at Asriel's terror.

Asriel eventually unhid himself and laughed with Chara. "Golly, that sure was a creepy face you did!" he exclaimed. "How did you do that?"

"I dunno," Chara responded. "Was it a good story though?"

"It was! You sure know how to tell a creepy story!"

Chara giggled again and said, "Thanks. We should probably clean up the bed before Mrs. Queen Mom gets mad at us."

"Yeah, you're probably right. Let's clean up."

The next afternoon, Chara was sitting on their bed, knitting something when Asriel came in. "Look what Mom just gave me!" he exclaimed, holding up an old video camera with the lens cap on. "She said we can go out and play with it. Come on!"

Chara hopped off the bed, knitting abandoned as they chased after their brother. The two children ran through New Home until they reached Hotland. "Where are we going exactly?" Chara asked.

"Waterfall!" Asriel exclaimed. "There's a really nice place where we can play with the camera!"

The two rode with River Person ("The water is very wet today.") and got off at Waterfall. "Follow me," Asriel said. He led Chara to a patch of Echo Flowers, but continued waking. Eventually, they came across a small hill that overlooked the flowers, but wasn't close enough for them to be heard.

"This is really pretty," Chara said. "I love how the Underground looks."

"Mhmm! Dad says the Surface is really pretty too though…"

Chara could see Asriel's face fall and said, "Oh, it's not that nice. I like it down here more."

"Really? You don't miss anything about the Surface? What about your family?"

Chara shook their head and looked off until the distance. Asriel knew they weren't going to get any more out of them, so he turned his attention to the camera.

"I still wanna play with this camera though," he said. "But what can we do with it?" The young goat monster then remembered what Chara had shown him the previous night and said, "I know! Chara, can you do your creepy face?"

"I don't know…" they hesitated."I don't like showing my face on cameras. You know that."

"Come on Chara? Please?"

Chara looked at Arial and saw he still had the lens cap on the camera. They smiled, knowing he didn't realize this, and said, "Okay, I'll do it."

"Yay! Let me turn the camera on." Asriel pushed the record button, still not realizing the lens cap was on.

"Okay, Chara, are you ready? Do your creepy face!"

Chara made the same face they made last night, with their eyes turning black and they let it an evil laugh.

"AHHHHHH!" Asriel exclaimed, jumping back. Chara's face returned to normal and they both giggled, "Hee hee hee!"

Asriel looked at the camera and said, "Oh! Wait! I had the lens cap on…"

"Well, oh well," Chara said. "That's that I guess."

"What?! You're not gonna do it again…? Come on, quit tricking me! Haha!"

Asriel turned off the camera and looked at Chara, who was staring out at the field of Echo Flowers. "Chara, can I ask you something?" he asked.

"What is it?"

"Why did you climb the mountain…?"

Chara turned to him and asked, "" What?!"

" Why did you climb the mountain Chara? Don't the humans know we're down here! Why did you come here? It's been over a year and you still haven't said…"

"It's not important," Chara said bluntly.

"But-"

"It doesn't matter Azzy," they said, cutting their brother off. "I'm here now, and that's all that matters."

"Why won't you tell us? Was it something bad?"

Chara sighed and looked out at the flowers, not wanting to face their brother. "I didn't climb the mountain for a happy reason. That's all I want to say."

Asriel said nothing and Chara figured he was done with the subject. They were surprised when he wrapped his arms around them in a hug. They wiped a tear from their eye that they hadn't realized came and sighed.

"Don't tell Mister King Dad or Mrs. Queen Mom, okay?" they asked Asriel, not moving from the hug. "I don't want them to worry."

"Alright," Asriel said, nuzzling his face against Chara's. "I'm sorry you came here for not happy reasons. But I hope you're happier now then you were up there. If you never want to say why you can't down here, I get it. I'll stop pushing you. But I just want you to be happy. We all do. Me, Mom, Dad, all the monsters down here. We just want you to be happy Chara."

Chara sighed again, their red eyes still staring out at the field of Echo Flowers.

"I am."

Okay, so I kinda wanna try and keep the reason that Chara climbed Mt. Ebbott vague if possible. I know that Asriel says that he knew why they climbed the mountain at the end of the True Pacifist playthrough, but I want to keep the reason vague since part of the reason Asriel never truly says why in the game is so that players can make their own interpretations. Whatever reason people want to believe Chara climbed the mountain is up to them, and I don't want to say one definitive reason for them climbing the mountain. It could have been multiple things, multiple factors, but that is up for the player of the game to decide for themselves. Same goes for Frisk. However you want to interpret the reason these two humans climbed the mountain is up to you, the player, to decide for yourself.