Astronomical

Unfortunately, as happy as they all were to find each other, after a few days of earthbending training while camping at the ghost town, it was decided they needed to keep moving to continue the war effort and not be sitting turtle-ducks.

And since Appa would be overcrowded, and Ty Lee wasn't about to give up Peacock the Second (the face Sokka made when he heard that name had been priceless), it was concluded that they would have to split up again.

"TomTom and I are going with Ty Lee," said Mai with no room for argument.

"Like we expected anything otherwise," said Zuko dryly. Ever since reuniting, the two would sneak off on their lonesome at least once a day (though, thankfully, as a mercy to Toph's feet, they would go into one of the ghost town's buildings to make use of the wood floor).

"Perhaps it would be best if those of us from the Fire Nation stuck together for now," Iroh suggested. "Traveling with the Avatar would draw attention, but a family seeking their fortunes elsewhere would not draw any eyes."

"Fine, but we're having a concrete meeting spot this time that we all know hasn't been taken over by the Fire Nation," said Sokka firmly. "No more of this blindly wandering around hoping we find each other."

"But where should we go?" asked Aang.

Sokka looked thoughtful. "To be honest, if we want to win this war by the end of summer, we need to start doing more things about it. It'd be a big help if we could get the Earth Kingdom and Water Tribe on our side for something that would let us get Aang close to the Fire Lord so he can be beaten. So maybe Ba Sing Se? "

All those from the Fire Nation exchanged a glance at hearing that.

"You know something, don't you?" asked Toph, sensing that look.

As he was the prince in line for the throne, Iroh, Ty Lee, and Mai all looked to Zuko, silently agreeing to follow his lead on what they do next.

Zuko looked conflicted but then sighed. "There is an event happening before Sozin's comet that would leave our nation vulnerable. One that could give you an edge if the Water Tribe and Earth Kingdom wanted to invade" he admitted. "It's a closely guarded secret, and one we've been able to keep because the event is so rare."

"Well, what is it?" asked Katara.

But Zuko shook his head. "I'm not going to tell you," he said.

Before anyone could get miffed, Zuko quickly added, "It's not that I don't trust you! It's that I don't trust anyone else who would be involved." He glanced at Mai and Ty Lee. "After a hundred years of hating us, I can't trust that the rest of the world won't do to us what the Cultivation Sects did to the Wen clan after the Sunshot Campaign. I'm not going to tell any weaknesses until all leaders involved sign a contract and swear an oath that the civilians will not be harmed, and those involved in the war will be judged fairly on a case-by-case basis."

Katara looked insulted. "Really, because that doesn't sound at all like you trust us," she said.

"I don't trust that anyone with a grudge won't take the information I have and prepare to use it for their own vendetta, and I don't trust that the innocents of my people won't get caught in the crossfire if not being the intended victims," Zuko insisted.

Katara looked like she would protest again, but both Sokka and Yue stopped her with a hand on each of her shoulders.

"He's right Katara," Sokka said. "We don't know the Earth King. We don't know his generals. We don't know what they'd do if they suddenly had some power over the Fire Nation's people. And while I know Dad wouldn't order anything bad, a lot of men in our tribe lost someone to this war and are angry about it."

"I doubt my father would order anything dishonorable either, but Hahn is still well-liked among my people," said Yue. "I know if he heard about a chance for glory he'd be able to rally enough forces to do something terrible."

Katara still looked obstinate but was starting to back down. However, they could all read the protest she wanted to shout all over her face.

'But we're the good guys!'

"There are rarely any good guys or bad guys in war," Ty Lee said, making Katara turn to look at her. "Your enemy can seem evil, and maybe some of those you're fighting are needlessly cruel, but most Fire Nation soldiers are just people doing their jobs, providing for their families, or fearing retaliation if they speak out. There are harsh punishments on one's whole family for those who disagree with the Fire Lord, and few dare to go against the grain to do it."

"Like JeongJeong?" asked Aang.

"Admiral JeongJeong had no family ties left when he deserted to bear the consequences of his actions, and it was his choice to take that risk," Iroh said gravely.

"But if anyone from the Fire Nation captures him, he'll be made an example of, and it won't be pretty," said Zuko.

"We've seen this happen before," Mai agreed. "We agree the Fire Nation has to lose this war, but we want the fallout to be better this time."

Their stony determination gave Katara pause. "What happened for you?" she asked. "You weren't exactly clear about that."

Iroh, who had gotten the whole story, looked grim.

Ty Lee and Mai looked over at TomTom sadly. "In the end, our son was the only Wen left alive," Ty Lee said, cuddling the toddler to her. "And he only survived because people thought he was Lan Zhan's baby instead. Being a baby Lan was much safer than being a baby Wen. He spent the first several years of his life hearing only of the bad of his own culture, none of the good."

Aang, who was the only airbender left alive, felt that viscerally. He couldn't imagine having to give up airbending, hiding his tattoos, and pretending to be another kind of bender just to survive. It was something he could easily do as the Avatar, but the thought felt like cutting off one of his limbs.

Katara, meanwhile, almost couldn't believe the Water Tribes and Earth Kingdom could be that cruel, but then she remembered Jet and his Freedom Fighters destroying a village. She remembered crazy General Fong and his obsession with the Avatar State at any cost. She remembered the people at the Northern Water Tribe that had called for the prisoners taken in the invasion to be made examples of. As much as Katara hated the Fire Nation for what they did to her mother, she couldn't stand the thought of some other kid out there going through what she did, Fire Nation or not.

Sokka, meanwhile, was more focused on the future. "This information you have, it's really good enough to hinge a whole invasion on?"

"It's the darkest day for the Fire Nation," said Zuko seriously. "It only happens for us every eighteen years or so. Most don't even know about it. It's rigorously tracked and any mention of it to non-Fire Nation citizens carries a death sentence to their entire bloodline. The fact that one of these days is happening just before Sozin's Comet is just… the odds are literally astronomical."

Sokka nodded. "Then we meet up in Ba Sing Se," he said. "We'll get that contract from the Earth King. Track down the Water Tribe fleets and make the chiefs sign it too. And then, you tell us that information your people think is worth dying for."

Zuko nodded back. "Sounds like a plan."

A/N They did learn from the past.

So, no library episode. Wan Shi Tong gets to keep his library in peace, and that researcher guy may find it someday, or maybe he won't, but if he does he probably gets to enjoy it the way it was meant to be without it sinking into the sand by an offended spirit.

Yeah, Zuko and the others are talking about the eclipse. Given that the Fire Nation has those celestial calendars, I'm willing to bet they knew the eclipse was coming, but the fact that having one makes them lose their bending is a closely guarded secret, especially against outsiders during the war.