Previously On Blood, Silk, and Steel
From Chapter 6:
Lu Ten suddenly tackled his father in a fearful embrace. "Don't leave Dad. Lord Agni wishes you to leave, but he will not stop you from staying. If you turn back, it will be hard. Stay with me and Mother. We can be a family again."
The old man took his son in his arms as well. "If I turn back, will I return to this place?"
"Of course Father, in time."
Iroh breathed heavily, then let go of his son. "Then, I am afraid, I must go."
Lu Ten let his father go and smiled sadly. "I knew you would say that; I had hoped you wouldn't. Your decision is wise and selfless—Lord Agni will be pleased, but I must take something from you to show him." Iroh closed his eyes and nodded. "Forgive me Father," Lu Ten whispered as he raised both his hands to his father's face and took the trophy Agni required. "Now—
"Live!" Zuko ordered, and so Iroh did.
From Chapter 29
I have come to a resolution. I will not have the Spirits steal from me. I am Iroh. I carry
within me the blood of Agni and Sozin and Azulon. I am fire. Who are the Spirits to judge
me, when the worst I have done is no crime, but only the product of my most heartfelt
love? I swear it, upon my Lu Ten's grave, upon - - - - - - - - - - - - - - - - - - , the Spirits
will tremble at my coming, will regret the audacity they had, to think that they could steal
my son from me.
I am coming, and even Koh will pale in comparison to my fury.
Lu Ten, you will live, you will rule, and you will end this war.
From Chapter 31
There were many myths of Agni. And in each, he wore a different face.
There was the selfless Agni, who had cut his veins of his own free will to mingle it with the blood of his brethren to make clay. The selfless Agni, who, when making men took for himself the challenge of fashioning two things: the mind of man, to dream, and the hands of man, to let man bring dreams to life. The selfless Agni who cooked the clay as the other spirits did their part to bring it to life.
There was the clever Agni who tricked Koh into taking the lesser sacrifices and kept man from starving by it.
There was the tender Agni, who loved Tui and kissed her every night.
There was the howling Agni, who swore enmity against La when the later refused him his sister's hand in marriage.
There was the clever Agni, neither selfless nor tender, who scorned by the Moon took a mortal bride and on her sired a son to whom he gave three gifts: a scroll and brush with which to safeguard knowledge, the skill of fashioning metal into useful object, and a pet dragon to teach the child how to master knowledge. There was the clever Agni, who did not howl, but rather took his son, learned in writing, metalwork, and firebending, and in calm and soothing tones explained, "You are blood of my blood. And as I have given you blood, you shall repay me in kind."
Agni wore as many faces as his brother, friend and foe, enemy and ally, Koh.
What face had he shown Azula?
And why had he shown his face to her?
Iroh would have given anything to know, but he had nothing left to barter.
And now, onto our feature presentation:
Zuko sat up, or tried to. The fever had broken, but it had left him exhausted. Weariness lived in his muscles, and as he tried to prop himself up his elbow gave out and he fell back on the cushions. At least they were soft, he thought, though he wished it weren't so dark or so cold. It was freezing, and he couldn't see anything. He let himself lie back and breathed hot fire into the night, warming himself up and bringing light into the room if only for a moment.
He knew there was no hope of getting to the fireplace himself. He tried to call out, but his voice failed him. His throat was dry and the words rasped in his throat. He could barely hear himself—he was sure the nurses outside wouldn't.
So the fireplace was not an option. He turned his head towards the dresser. It was a foot away from his head, but he couldn't see anything on it, the room was so dark. Getting his arm to move was an ordeal, all of him felt like it was made of lead, or like lead that could feel pain. But eventually he managed. Blinded by the darkness he felt around until he knocked over a candle. He set it upright and felt his way up the candle until his thumb and index finger held the wick, and finally, there was light.
"Careful, Nephew," he heard his uncle call.
"Uncle Iroh?" he asked.
Zuko wondered how long his uncle had been in the dark with him. Why hadn't his uncle had the fireplace lit? The light—there was something about light—Zuko couldn't remember. But the dark—
"It's dark, Uncle."
"So rest your eyes," his uncle answered.
"I'm cold, Uncle."
"A little cold never hurt anyone."
Zuko shivered. He fumbled for the candle. His uncle did not help. The candle fell and the fire caught on the tapestry on the wall.
His uncle did not move to put the fire out or reign it in, and Zuko was too weak to put it out. The fire danced and cast shadows about the room, though it seemed there were some places where the light could not reach and the dark remained.
The light caught in his uncle's golden eyes.
A thought nagged at Prince Zuko, but he couldn't quite remember what it was that bothered him.
"Rest Prince Zuko," his uncle's voice told him, but Zuko couldn't sleep. He was afraid of the dark.
Zuko's fever would not abate. The fire was coming from within, and even Azula could not pull it out. Yue and the island doctor had been tending to the Prince for hours, but it seemed like there was nothing to do but keep the Prince as comfortable as they could.
After three hours, Azula got up with a yawn.
"Ling will be here in the morning. Make sure my brother is here to greet him then. I'm going to bed. If my brother's condition worsens, wake me."
Sokka would have liked to leave too. But Zuko was his only ally in the Fire Nation Court. But if there was one organ in Sokka's body that held more influence over the savage than his cunning mind, it was his growling stomach. And at three in the morning, hunger finally overtook him.
"I'm going to the kitchen for food," he announced. "Does anyone want anything?"
"Coffee," the Fire Nation doctor said.
Yue simply shook her head as she pressed the wet sponge to Zuko's face once more.
"You should eat," Sokka told her. "Actually, you should go to sleep."
"No, it isn't," he disagreed, but he argued no more with her and left in search of sustenance.
The kitchen staff was all asleep, and as Sokka wanted silence, he didn't bother waking them. The kitchen itself was dark, and cool, a welcome respite from the heat of Zuko's bedroom. The light from his lamp was dim, but good enough. There was no reason, he thought, to bother lighting the kitchen lamps.
He found some stale fireflakes and downed them at once, but the small amount of food only whetted his hunger more. He searched around until his found some mango. It was good and ripe, he could see, so he peeled and cut it into a bowl and set it aside for Yue. He was almost certain he could entice her with it.
For himself he found some dried sausage—not quite the whale-cow jerky he loved, but close enough to make his mouth water.
All he needed now was the coffee for the doctor. After fifteen minutes of searching, he had managed to find some whole beans, but no grounds. He ground some in a mortar he found, and then, with the fire from his lamp, he lit the stove to boil water.
The small flame ballooned into a bonfire for a second, enough to singe his eyebrows. He yelped in surprise and fell back, stumbling over his feet and falling on his arse.
He didn't need Azula's giggle to know what had happened, but the Princess giggled nonetheless.
"I knew you'd come here, sooner or later," she said, dangerous amusement running through her eyes.
He shrugged, ignoring the burning sensation in his face. No serious damage had been done, but he fully expected to have something that looked like a bad sunburn in the morning and was hardly looking forward to days of peeling layers of dead skin from his face. "A man's got to eat."
The amusement left her eyes and the flame in his lamp flickered dangerously. "Did you poison my brother?"
He barked out a laugh. "Of course not. I love the Prince very much. He's like a brother to me."
"As someone who has a brother, I know that doesn't mean very much."
"Well then, my darling wife to be, what can I say? He was fine all day with me. He only fell ill after he had dinner with you…"
That made her angry. Sokka didn't care, she was already angry, and Azula did not know feelings in moderation. What more could she do? Try harder to murder him? She was already trying her hardest. He put the kettle on the stove.
"If you think murdering Zuko is going to get you back in my good graces—
"Azula. Darling. Light of my life, apple of my eye, heart of my breast. If you think I'm stupid enough to think you have good graces, frankly, I'm not sure why you trusted me so much. If I poisoned Zuko, I would do nothing more than eliminate my only patron at court and give you that excuse you want so desperately to tie me to the stake. You weren't grateful to your mother for giving you life, why should I expect you to be grateful to me for giving you the crown?"
"I am going to have so much fun, listening to you scream as you die."
The water was done boiling, so he poured it over the grounds. "Oh, baby, the things you say when you're worried about your big brother. I only wish Katara felt so warmly towards me. But you needn't worry, I'm sure he'll be alright. If neither you nor Yue nor the doctor can get his fever down, I'm betting it's not a disease of this world. Or maybe it's just sunstroke and too much drinking. But he'll be alright soon enough, and it'll be a happy day for the Fire Nation when it still has its Crown Prince, waiting there, in front of you in line."
He didn't wait for Azula to answer. He took the coffee and the mango and went back to where Zuko was burning up.
The darkness was eating the fire, and with it the heat and the light. And it was all Zuko could do to keep the fire going.
"Prince Zuko, sleep," his uncle said, "stop bending the fire. You'll tire yourself out. Sleep. Rest."
Zuko was in the habit of ignoring his uncle. Of fighting with his uncle. The last time he had fought with his uncle—
The darkness was eating he fire, and with it the heat and the light. The darkness was surrounding him, and all he could see was the glint of his uncle's eyes.
The last time he had fought with his uncle.
The fire was glinting in his uncle's eyes.
His uncle didn't have eyes.
Sokka was handing the mango to Yue when Zuko gave a frightened yelp.
A single syllable escaped his lips. Through it all, his face didn't betray the emotion of his fear.
And then the fire went out, and the room, which had been scalding and humid, became colder than the North.
"You know my name. You spoke it, just now. You know who I am, and you should know you can't hide from me in the dark, Nephew."
"I'm not your nephew."
"Oh, but you are. Aren't you? You are a son of Agni. That makes you my nephew."
"Why are you here?"
"I wanted to see you, Nephew of mine, child of Light, only son of Ozai."
"My Uncle's face—
"Ah yes. Agni's most favored son. It hurt my brother to part with it, but I was owed a debt, and little Agni always did know what I liked best."
"He's not," Zuko answered, his voice sounded small in his ears, and he wasn't sure if it was the vast expanse of dark and cold eating up his voice, or if it was him, squeaking like a child. He felt like a child. "My father is. Agni's Most Favored Son."
Koh chuckled, and even in the darkness—there was no light at all—Zuko could see the spirit's face contorting. The expression did not suit his uncle's face. "Is that what you think, Nephew? No. No. Ozai sits on the throne by Agni's grace, but not by any special love my brother has for your father. Your Uncle, my baby brother's pet, oh, he was a naughty, naughty boy. So Agni punished him. Because that's what parents do, when their children misbehave. They punish them, even if it hurts."
"You're a liar."
"Of course. All too often, parents don't punish their children when they misbehave. That's why the lot of you are as delightful as you are. Your sister, for instance. She's delightful, isn't she? Agni thinks so. If he weren't so set in his plotting, I think he'd take her for his own.
"I can't say I'd blame him. She has such a lovely, lovely face. Who knows? One day, perhaps I'll take her, if my brother won't."
Zuko shivered and the dark closed in around him. But he was careful to keep his expression blank. He ignored the comment about Azula. If he thought about it, he would… he wasn't sure what he would do, but he was sure he would be lost.
"Why are you here?"
"Oh, relax, little Nephew," Koh cooed. "I'm not here for your face. Perhaps before I would have been interested. But now, I'm afraid it's too unique for my collection. It has no resale value. Not, that I ever sell my pretty, pretty faces. But, then of course, there's the rub."
A mortal man would have stirred Zuko to anger with those words. The prince merely nodded and kept his face blank.
"I have a certain weakness for older brothers who are outshined by their brilliant younger siblings. You think you have it bad, Prince Zuko? Think of me. Your sister is the Daughter of the Dawn—my brother is the Sun. And I am the darkness from which came the light, I was here before, and I will be here after, and never, ever, have I had a temple built to me. 
"And you… will you ever have a song written about you?"
"I don't want songs."
"That's a difference between you and your sister. And why I like you. You're fine with quiet anonymity. All you want is to make the world a better place. And all she wants it to make it hers. You're like night and day. And you're the one with all the good intentions. I wonder, how you ever managed, with Agni's blood in your veins."
"And you like good intentions?" In the stories, Koh's dark heart gobbled the dark hearts of men. It never occurred to Zuko that the Spirit might be granting respite to the good out of charity rather than lack of power over the righteous.
"Of course, Nephew. Good intentions are the best stones for paving the road to me. And no one's intentions are better than yours. You intend, for instance, to build a temple to Agni. Build a shrine to me. Agni's massive temple sprawling in the east will bring my baby brother joy. To me, you will build a shrine. A tiny shrine on the westernmost cliff in the Fire Nation, and you'll build it with you own hands, where a loose stone will drop a traveler into the sea to be smashed against the rocks. You will build it there, and you will tell no one what you have done.
"What good is a shrine that no one will visit?"
"It's no good at all, and that is precisely why I want it."
"And if I refuse?"
Koh chuckled, but it wasn't a threatening chuckle. "Nephew, you promised my brother a temple because he saved your Uncle's life. Agni would have done that of his own volition, if he could, but he couldn't. The souls of the dead don't belong to the Kindling Flame.
"A shrine is a small price to pay, don't you think, for your uncle's life?
"That's all I ask. Everything else that you must do for me you will gladly do, without my ever needing to ask. Your kind heart will do my work, and I will love you for it. Don't waste this gift, my beloved Nephew. Build this shrine, and cold and dark will never harm you.
"As to light and heat, however? There I can make no assurances."
In her life, the Lady Toph had been on a boat twice. And she was beginning to notice a pattern. She hated water.
General Iroh had told her they were going to a place called Ember Island. It sounded like a horrid place, at least from the name of it. But the General had assured her that it wasn't, and told her that embers could be beautiful, and he'd gone on to describe them in words that sounded lovely, but meant nothing to her, because she had never seen an ember, or anything else, in her life.
She didn't know whether he was right, whether embers were beautiful, or if old Iroh thought so because he was a crazy firebender, or if he was lying. For all she knew, they weren't heading off to Ember Island at all, but sailing off the edge of the world.
What she did know was that there was a storm going on outside. The whole boat was cold, and the water was tossing them about. Her furniture was nailed to the floor, so at least it didn't move, but one particularly vicious wave had thrown her off her bed, so she's crawled into a box she'd found and was holding on to it for dear life and doing everything in her power to keep her supper in her stomach.
She wanted to cry, but she refused. The Fire Nation had made her cry enough, and she was sick of it. She was sick and tired of feeling like the invalid her parents had always made her out to be, and she wasn't going to let them make her feel like that any longer. One way or another, she was going to get away, even if she had to raise the ocean floor above the waves and make a bridge back to Gaoling to do it.
Thunder clapped and Toph's grip on the box's sides tightened. A knock at the door echoed the thunder. "May I come in, Lady Toph?" Iroh's voice came through.
Toph was torn. On the one hand, she Iroh was a man who had burned down a third of the Earth Kingdom and her jailer. On the other, he was growing on her. And then again, that was all the more reason not to see him. And then again, she knew he would come in anyway.
In the end, she told him he could come in if his guards waited outside. She could deal with Iroh in her dark, but she didn't want his lackeys to see her hiding in a box.
The door opened and closed, and she heard his footsteps. They were remarkably light for a man his size.
"Are we going to capsize?"
"I hope not," he answered.
"I don't know how to swim," she admitted. It didn't matter much. Zuko knew, and she imagined Iroh knew what Zuko knew (though of course, not the reverse).
"That's alright. I know how to swim. If we sink, you can ride on my back, as if though I were a giant tortoise-hare."
The thought made her laugh, and then she realized she was laughing with her jailer and bit her lip. But the silence was dreadful—the only thing to fill it was the anticipation of the next clap of thunder, so she spoke again, "I've never seen a tortoise-hare."
"They have them at the aquarium on Ember Island. I can take you to see them. I can even arrange for you to ride on one. They're fantastic creatures. Hard and smooth when they're wet, and soft like nothing else when they're dry."
And like that, Iroh talked through the storm. His voice a soothing contrast against the storm that raged outside. He told her about animals he had seen and ridden, places he had visited, and stories he had read.
Some of the stories she knew. He told her how the spirits came together to make the race of men: The Spirits bled to make the clay of man. Feng provided earth to make man's body, La gave water to give the body shape, Yang blew breath into man's lungs, and it fell to Agni to cook the clay with fire.
But then Iroh added details she hadn't heard before, and she wondered if the Fire Sages had made them up to make the Lord of Light look good, or if her tutors had left them out to achieve the opposite effect.
Iroh said that Agni had at first refused to cook the clay. "If I cook him now," Agni said, "he will be like all the other beasts. But there are enough beasts." And so, Agni thought and worked, and fashioned the mind of man, to dream and the hands of man, to let man bring his dreams to life.
He talked of how Koh opened Man's eye to his loneliness, and how, from her perch in the sky Tui saw the Man's tears, and took them to Agni and told the Lord of Light that he was cruel. And the Lord of Light laughed and worked with Tui, until Man had Woman, Agni's heart was Tui's.
And that was all that Koh had wanted, because the demon loathed his brother.
Azula was not yet asleep when Sokka burst through her door.
"It's Zuko!" he told her with little explanation, and took her by the hand and dragged her to her brother's room.
The fire had gone out and the room was freezing. In Ember Island in the summer, it was impossible.
"What in Koh's name is this?" she asked.
"That's exactly it," Yue answered solemnly. "Koh."
In days gone by, Azula would have laughed at the thought, taken it as nothing more than mere superstition. But if her recent adventures hadn't quite taught her to fear and respect the spirits, it had at least taught her to take them seriously.
"Have you tried to light the candles?" she asked.
Sokka nodded. "They won't light."
"Oh, yes they will," she said. She opened her palm and called forth a flame. It should have been blue and massive; it came out small and yellow, but it was something, and in that moment, Azula knew no one but her could have brought fire into that room. She dropped the fire onto a candle and set it by Zuko's bedside and sat beside her brother.
"Doctor, thank you. My carriage will take you home."
"Doctor, do you know anything of spirits?"
"Then you've done all you can. The Fire Lord thanks you for your service. Good night."
Once the doctor was gone, she turned to Yue. "Do you know anything about the Spirit Koh?"
Yue shook her head. "Only that he is Lord Agni's brother, the oldest spirit and the first demon."
"Well, then, let's hope Zuzu's not stupid enough to give him what he wants."
Iroh normally allowed his sailors to go to land first. But the water made Lady Toph so anxious, that this time he made a point of taking her onto terra firma himself before anyone else descended.
Three paces onto land, and suddenly there was a great commotion. He knew something was happening, assumed it was bad, and had no idea what it was. It made him feel like an old cripple, reduced as he was to crying out, "STOP!" and asking for an explanation.
"The Earth pig—
"Lady Toph," he interrupted. "Her name is Lady Toph, and she is my guest, and you will respect her as you would respect me."
"Lady Toph," a soldier started through gritted teeth, "attacked a subject of the Fire Lord."
"Lady Toph?" he asked.
"He was running towards us, and armed. I thought he might mean to do us harm. But I didn't hurt him," she said, then added, "although I could have, if I had meant to."
"He was in uniform," the soldier explained.
"Well, a lady of the Earth Kingdom can be excused for thinking a man in a Fire Nation uniform running towards her means to attack. Lady Toph, could you release the soldier?"
Toph grunted her displeasure at the request, but she moved her foot and the earth around the man fell away. The soldier stumbled forward but caught himself before falling.
"General Iroh, sir, it's your nephew, the Prince—
In days gone by, Iroh wouldn't have hesitated to jump on a komodo-dragon and ride off to the royal residence as fast as the beast would carry him. But now, he had to order a carriage.
"Yes, of course, General Iroh, we'll get one ready—
"Why isn't it ready already?" Iroh asked, enraged.
"We didn't think—
"That's exactly right!" Iroh shouted, and the soldiers there, who had heard tales of the Dragon of the West, but had never seen anything other than a fat old lord, suddenly believed that this could really be the man who laid siege to Ba Sing Se and breached the outer wall.
"Tell me how to get there," Toph said, feeling Iroh's heart beat quicken with anger and fear, "and I'll take you there."
Iroh didn't hesitate, and for many years to come, the people of Ember Island told the story of the day General Iroh rode a mountain with a girl through the city streets.
Azula ordered Yue and Sokka to bed and kept vigil over Zuko by herself through the night.
As the dawn began she remembered Agni's words. "But you helped me resolve a debt, and so I will help my Most Precious Child. I will help you, once, twice, and three times. No more, no less. Azula will call for me, and I will answer, three times."
He had helped her once. Or had that time in the North not counted? She wondered what would happen if now she knelt before her brother and prayed for Agni to wake him.
But she didn't do that. She simply sat by his bedside and waited for the sun to rise, and as it did, the flame on the candle grew, until, at last the sun was up and the flame was blue, and only then did Zuko open his eyes.
Iroh arrived to find his nephew eating breakfast with a voracious hunger. For once, even Sokka was impressed by the amount of food the Prince was packing away: hot cakes and eggs and honey-spiced ham with mango and papaya and pineapple.
"I was told you were ill," Iroh said.
"I was told the same thing," Zuko answered cheerily as he took another slice of ham off the table. "But I think it was just sunstroke."
No one at the table opened their mouths to contradict him, although even without eyes, Iroh could feel a certain crackling tension in the air. Toph could feel it too.
"Join us for breakfast," Zuko said, and Toph and Iroh did.
Later, just before she got up, Azula asked, "Brother, did you have any dreams?"
"If I did, I can't remember them."
Toph felt his heartbeat shift and knew he was lying, but couldn't imagine why he would lie about something so petty.
"Are you sure you're alright?" Iroh asked. Immediately after breakfast, Zuko had dragged Iroh to the library.
"I hope so, Uncle," Zuko answered. He found what he was looking for, a map, and unfurled it out on the table.
"The westernmost island in the Fire Nation, is Sunset Island."
"But it doesn't have any cliffs, does it?" Zuko asked.
"What is the westernmost cliff, do you know?"
Iroh nodded. "It's on Fei Nisi Tai Er. The face of an old, inactive volcano. The whole island is made of obsidian and nothing grows." 
"Yes," Zuko nodded. "That sounds about right."
"Oh, it's nothing," Zuko said, and Toph could tell he was lying again. "Well, that's all I wanted to know. Thank you Uncle."
"Zuko, where are you going now?"
"To meet with Pu On Tim."
"What do you want with that talentless hack?"
"Oh, you'll see."
A/N: This was an odd chapter. It took me forever to get past the first paragraph, then I wrote the rest of it in 2 days. Surprisingly, I'm pretty happy with it. Though, it's been a while since Azula did anything really awesome. Her super power seems to be speech-writing.
 – Koh in this story fills a role akin to that of the Christian devil, although Agni has some devilish things too—basically I'm treating the Spirits as Greek Gods—at least the major ones. But the idea that Koh would be Agni's older brother is inspired, particularly, by Goethe's treatment of Mephistopheles, in particularly these lines from his introduction:
I am part of the part that once was everything,
part of the darkness from which came the light,
that haughty light that envies Mother Night.
 – The backstory between Koh and Agni is somewhat modeled on a Neil Gaiman story about Desire and Dream. I think it's in Endless Nights.
 – According to Google, this is the Chinese way of saying Finisterre—World's End.
 – Google Pu On Tim, if you don't know who he is.