It wasn't that Sokka didn't believe in all the spirit mumbo-jumbo, it was more that it was not his style. But being taken by a huge monster into the spirit world and leaving at the very last second, there are some lingering effects that he simply can't ignore.

Winter Solstice: The Spirit World

"That's it! He needs help!"

"Sokka, wait!"

Sokka ran outside without heeding his sister. Everyone else was fine with leaving Aang to face Hei Bai alone, but he sure wasn't. He wasn't just going to sit by as his friend was throw around by it.

"Hei Bai!" he raised his boomerang in preparation to throw. "Over here!"

Sokka threw his boomerang, it simply bouncing off Hei Bai as if it were a pebble. He quickly sprinted forward towards Aang, surprisingly unafraid of the massive spirit.

"Sokka, go back!" yelled Aang.

"We'll fight him together, Aang." Sokka said, turning around to see that Hei Bai had vanished.

"I don't want to fight him unless I-" started Aang.

Suddenly, a huge hand grabbed Sokka, yanking him away from Aang. Hei Bai squeezed Sokka tightly, severely cutting off his air supply, before spiriting back into the forest. Any confidence Sokka had previously vanished, especially when hearing Katara cry out his name fearfully. Behind Hei Bai, Aang flew on his glider, and Sokka held out his hand in hopes of being rescued.

"Aang!" he cried out. "Over here! Help!"

"Hang on, Sokka!" yelled Aang.

He flew in close, reaching for Sokka's hand. The tips of their fingers clasped, when there was a sudden flash of light, and then everything went dark. Aang wasn't there anymore.

Sokka opened his eyes to see that he was surrounded by tall stalks of bamboo. He looked around in confusion, trying to remember what had happened to lead to this. Nothing came to him.

Alright, what's the last thing that happened? He put a hand to his head to think. Aang was facing down Hei Bai and I ran out to help him... Then there was a blank. Aang was reaching for me for some reason.

Sokka grit his teeth in irritation. He reached for Boomerang to start cutting through the bamboo, but it wasn't there. That was concerning. He always had Boomerang, and he would have noticed if he had dropped it.

Well, nothing to be gained by standing here.

Sokka pushed through the bamboo, trying to not to let any swing back and hit him. Unfamiliar voices in front of him made him stop, and he leaned in to listen without leaving the sea of bamboo.

"Do you think we'll ever get back to the village?" asked someone nervously.

"Maybe," replied someone else dully. "Or we'll all just be stuck here forever."

"Don't say something like that!" snapped yet another person.

Sokka slowly backed away from the voices as he remembered what happened. Hei Bai had taken him, and Aang hadn't been able to save him in time. He must have been taken into the spirit world.

No need to start panicking. Aang will find a way to get me out. And those other people, too.

Feeling slightly less panicked, Sokka turned around and started walking in the opposite direction of the voices. Maybe Aang was already in the spirit world, and just ended up somewhere else. And even if the wasn't there was no point in just sitting around. There was probably somewhere he could explore.

Finally, he stepped out of the sea of bamboo. He had expected the spirit world to look weird, but it looked surprisingly normal. Sure, the sky looked purple and green, and some of the grass looked a bit blue, but that was about it.

A short distance away, there was a young man sitting on a rock with a fire burning merrily in front of him. He had black hair tied up in a ponytail on the top of his head, and was wearing orange and yellow. The colors of the Fire Nation.

Before Sokka could go back to the bamboo, the man spotted him, and raised a hand up in greeting. "Hey, man!" he called.

If he was a firebender, he could set all of the bamboo on fire. Feeling caught, Sokka cautiously walked over to him. "Uh, hey."

He jumped up as grabbed Sokka's hand as soon as he came close enough. "Name's Kuzon." He eagerly shook Sokka's hand. "What's your's?"

"I'm Sokka." He pulled his hand away. "So, uh, just to be sure, this is the spirit world, right?"

Kuzon's face fell. "Oh, you don't know?"

"Don't know what?"

"You died, and now you're here. So, yes. This is the spirit world."

Sokka put his hands up. "Whoa, I'm not dead!"

He sighed. "Yeah, it's always like that at first-"

"No, I was taken here by a spirit!" Kuzon raised an eyebrow. "I was trying to help my friend Aang stop Hei Bai and-"

"Aang?" Kuzon looked at Sokka with wide eyes. "As in Aang the Avatar?"

"Uh, yeah?"

"I knew he was still alive!" Kuzon was grinning broadly. "What training is he on? Has he made it to firebending yet?"

Sokka took a step back. "You know Aang?"

"We were friends! Are you adventuring with him?" Kuzon excitedly grabbed Sokka's wrists. "When you get back, can you tell him that I said hello?"

"Um..."

"Wait, maybe you can bring something back to him! I had a firebending scroll when I died, and you can give it to Aang to study." He started pulling Sokka towards a cave off in the distance. "Do you know how much longer you'll be here for?"

"Well the village wanted Hei Bai stopped before the solstice, so Aang will try to get me out before then."

"This will be quick!" Kuzon smiled. "Aang will understand if you're a bit late, anyways."

A glow came out from the bamboo sea, and Sokka frowned in worry.

Bamboo sprouted up where Hei Bai walked away. Out came people, looking confused and tired, and Katara's eyes lit up. Sokka was going to be there! As people greeted those who had been lost, Katara's smile faded away. Sokka wasn't there.

"Aang?" she asked nervously. "Where's Sokka?"

Aang frowned nervously. "I don't know. He should be with the others."

"Did something happen?" She gripped Sokka's boomerang tightly. Oh, Sokka, where are you?

Kuzon had been talking non-stop about Aang the entire way to the cave and back. Sokka held the scroll tightly in his hand, wondering if it would just be lost when he left the spirit world or if it would really come back with him.

"Kuzon!" yelled someone suddenly. "What are you doing?"

Sokka turned to see another person wearing Fire Nation clothes, but he was younger than Kuzon. "Lu Ten!" Kuzon frowned as the younger boy practically ran over to them. "What's wrong?"

Lu Ten pointed over at the bamboo, where the glow was starting to vanish. "There is a portal out of the spirit world open, and it's starting to close!" He then pointed at Sokka. "He needs to go before it's too late!"

Sokka's eyes widened fearfully, and Kuzon looked over at him with shame and worry evident on his face. "Oh! Sokka, hurry!"

With no response, Sokka sprinted off into the bamboo as the light vanished. Lu Ten glared at Kuzon, who looked down at the ground with guilt.

"Do you realize what you've done?" asked Lu Ten. "He'll be lucky to make it out of here with no effects from the spirit world."

"Like what?" asked Kuzon nervously.

"I guess you'll have to wait and see. You did basically make yourself his guardian spirit. You'll be sure to see him again."

Sokka stumbled out of the bamboo onto the ground, to be immediately grabbed in a tight hug by Katara. "Sokka! We were so worried about you! What happened to you?"

"I think I met a spirit." Sokka looked over at Aang, who was looking at him oddly. "He said his name was Kuzon."

Aang's eyes widened. "You met Kuzon?"

"He wanted me to give you something." Sokka looked down at his hand, only to see that the scroll was gone. "But I guess it didn't come back with me."

"I'm just glad you're back," said Katara.

Aang kept staring at Sokka, before shaking his head as if to snap out of some sort of trance. "Well, it's great you're back, Sokka. But we might have a problem on our hands. See, I need to talk to Avatar Roku..."

As Appa set off at a fast pace towards the Fire Nation, Aang could help but look over at Sokka once more. Something had clearly happened to him in the spirit world. There were very light, but still visible, blue lines running down Sokka's arms, almost like his tattoos, but with no arrows on his hands. Katara didn't seem to notice them, so clearly he could only see them because he was the Avatar.

But they would have to wait for another time. After talking to Roku, he would talk to Sokka about what had happened in the spirit world. For now, they had to hurry before the eclipse passed.

So this a pseudo-au, and mostly follows the plot of the show. Show-canon moments will be mentioned only in passing, and the main focus will be on how Sokka was effected by the spirit world.

Also, apologies in advance for any canon I'm breaking. I'm not all that Avatar-smart.