Disclaimer: Avatar, and all that it entails, is not mine, but Nickelodeon's.
A/N: This is nothing but fan speculation. But I thought I'd give some justification to the whole 'Agni' concept.
Agni's Kai
Oachto huddled in his blanket, shielded by camelephant hide against the darkness and cold. The wet season was upon his tribe, and with it came the sheer curtains of rain, blocking out the sun.
Sun. Oachto hadn't seen the orb of fire in days. Clouds swathed the sky in grey, chilling the sun warrior's spirit to the core. Hail had destroyed the maize fields and rain had washed out the trade roads. Moisture, he'd heard, had even seeped into the storage chambers, and could cause mold to grow upon the stored grain. Where would the tribe get their food from, this year?
Oachto pondered, listening to the rain pound on the hut's roof. The spirits were angry. That was the only explanation. But the stomp dances had been useless. The Chief was talking about perhaps sacrificing some of the slaves, to appease the Masters. The Masters, with their flight, could take the tribe's prayers to Agni… but their demands were high. If slaves did not satisfy them, the tribe's warriors would be next…
Unable to sleep, Oachto opened his eyes and walked up to the fire, stepping carefully over the sleeping bodies of his fellow sun warriors. Men and women both, they slept in circles around the central fire, presenting the greatest plane of their bodies to the warmth.
He stared into the flames. Give me a sign, Agni. Tell me what I must do to keep my tribe safe. Tell me how I can protect us.
The fire flickered and snapped, forming shapes of dancing figures, of birds taking flight. The smoke curled into serpents and strange faces, dissolving as soon as the eye lighted upon them.
But Oachto was no smoke-reader, no fortune-teller. Whatever the fire told him was lost. Like the fluting language of the sky shepherds, the spirits' messages were unintelligible.
The Masters would know. They always knew. But it was forbidden for any but the sages to talk with them. Surely they would not speak with a mere warrior?
The wind howled outside, and the fire flickered. Darkness began creeping in, entwining itself amongst the sleeping bodies like death itself.
Oachto blew on the fire and placed a log upon it, stoking it back into life. The Masters needed no wood for their fires. Flame leapt from their throats as it did from the mouths of volcanoes, and such fire! Such fire as one could dream into life! The pitiful blaze in front of him, in this stone hut in the center of a tribe drowning in rain, this was nothing, compared to the Masters. Their command of fire made the miracle of twisting sticks together look like a child's game.
Most warriors would feel humility, then. The Masters were greater than any man. One need only look upon them to see this. But Oachto did not feel humble, just then. He felt anger, and resentment. Why should the Masters have such power? Why would Agni bless them so, and not his devoted tribe?
There was a mountain, Oachto knew, one that reached beyond the heavens and to the realm of the spirits. It was many miles away, and went through the territories of the uplander tribes. But it was said that Agni himself slept atop its peak.
Oachto looked out, into the rain. They needed help, or they would starve in the coming dry season. And though he could not speak to the Masters, there was no specific taboo against speaking to Agni directly.
Oachto picked up his spear and shield, and went out into the rain.
The rain never halted, in all the miles of mountains and valleys through which Oachto traveled. He hunted wild dragon moose and cow hippo, and drank from flood-swollen mountain streams. He met the upland people, and though they spoke a different language, rushed and gobbling like the words were in a hurry, he could see that they were suffering. The rain had caused their fields to flood as well, and their steep mountain slopes to turn to mud and rubble. They looked at Oachto with mistrust in their eyes, but he put down his spear, and they let him pass.
Eventually, as the now weaponless Oachto climbed higher and higher into the sacred mountains, he met fewer and fewer people. The slopes became more open, the jungles of the lowlands giving way to pine, and eventually to scrub, then nothing but weeds and grass.
Oachto was crossing an alpine meadow one day, when a deep shadow fell across him. He looked up, and saw it. The great flying serpent, the Master of Fire, the blue dragon.
It landed in front of him, its great claws sinking into the ground, and looked at him with golden eyes.
Oachto was a great warrior. He was brave, and strong, and honorable. But never before had he looked into the eyes of a Master. His spirit quailed and his knees trembled under the gaze, which burned through him even in the rain. Now, he felt humility. He fell to his knees, and bowed.
"Why do you come here, Sun Warrior?" said the Master, her voice like the roar of wildfire.
"I have come to talk to Agni on behalf of my people," said Oachto. "We are dying from rain, and need His help to survive the coming year."
"Talk to Agni?" the Master appeared surprised. Then, she laughed, a sound like the thundering of a volcano. "Talk to Agni and perish, Sun Warrior. No man may look at Agni, much less speak with Him!"
"Please," said the proud warrior. "My tribe is my home, and without sun, our crops will not grow, and our homes will wash away. I must speak with Agni!"
"You are a fool to ask it. Agni has fire for blood, and He will not listen without argument. But I like your spirit. I will give you a gift to help you."
The Master leaned in, and breathed a hot breath onto Oachto's eyes. "You will be able to look upon Agni, and He will hear your voice. Good luck to you, Sun Warrior. But I look forward to tasting your ashes."
And with that, the dragon left, streaking into the clouded sky like a spear from an atlatl.
Oachto climbed higher into the mountains. He became short of breath, and light of head, but still he continued, over the slick rocks and rain-softened soils. But he could see the peak now, shining with light.
Oachto climbed and climbed, until he reached Agni's palace. There, he was struck speechless. Never before had he seen such a mansion of gold, so large it made the dragons circling it look like sparrowmice.
He waited there, outside the palace, until night finally fell. He could see the sun setting, and indeed, he could now look at it without pain. It floated down from the sky and landed inside the palace walls.
Oachto approached the gates, and found them unguarded. He quietly entered, and beheld Agni.
Ah, how even to describe the Spirit of the Sun, whom no man may look upon? The blue dragon had been awe-inspiring, immense, incredible! But next to Agni, she was as a gecko monkey. Agni, feathered serpent, luminescent, beautiful! Agni, the life giver! Agni, the golden dragon with a thousand eagles' wings.
Agni was curled into a disk, his coils entwined, a great fiery ball of feathers and scales. He hardly seemed to notice Oachto, a mere insect silhouetted against the Sun Spirit.
Oachto bowed, his forehead touching the floor, frightened for his life. But then he remembered his children, shivering in the cold, and remembered his purpose. "Agni…" he said. "Hear me, oh Agni."
Who speaks? said Agni, and Oachto's body trembled with the sound.
"Oachto of the Sun Warriors speaks, oh Agni."
Then, Agni's head turned, and beheld Oachto with eyes the color of lightning. What brings you here, Oachto of the Sun Warriors?
"I have a request to ask of you, Sun Spirit. The rains are killing my people. I need your heat and light to heal our lands."
How dare a mortal ask such a thing of a Great Spirit? We are not your beasts, subject to your beck and call! We are not your fellow mortals, who you may speak to as an equal! We are your gods! You do not deserve anything from us!
I will die, thought Oachto. This is my end. But he wanted to die on his feet. So he stood, and faced Agni.
"We need your help! Without you, we will surely starve! You are the chief of chiefs, it is true, but even a chief must support his tribe! Or else, where is his honor?"
Agni turned His head slightly, as if thinking.
"Agni, allow me to prove myself to you, as an equal. Let me prove to you that I am deserving of help."
You wish to prove yourself, Oachto of the Sun Warriors? Very well, you shall. We shall meet at sunrise. Now leave my presence.
Oachto bowed, and left.
Oachto did not sleep that night. Instead, he carved an atlatl. Then, he knapped a blade of obsidian, and affixed it to a shaft of wood with cordgrass. All night, he sharpened it, until it could have sliced bone.
When grey morning shone through the rain, Oachto went back into the palace. There, in the courtyard, waited Agni. He now took the form of a golden-skinned giant, his hair and beard red as flame.
Come, Oachto of the Sun Warriors, he said. Let us see if you are equal to a spirit.
Fire danced around Agni's hands, then roared towards Oachto. The warrior gasped and dodged, but the fire moved as though it was alive, twisting in the air and following him like a wild beast. Agni made a gesture, and fired again.
Oachto's heart pounded in his chest, and he ran like a spooked jackalope. The fire crackled at his heels, tickling the backs of his legs with small burns, as though it was only playing with him.
This was foolish! How could a man fight such a thing? Oachto looked back at Agni as he ran, and saw… the Sun Spirit was moving, directing the fire with His arms and legs, though He was far away. If Oachto could hit the Sun Spirit with his spear, stop Him from moving…
But how could Oachto stop running long enough to do so? The fire would catch him! But he had no choice. He couldn't keep running forever.
Oachto put his spear in his atlatl, stopped running, and, as the fire engulfed him, he threw.
The pain was terrible, and the Sun Warrior screamed and burned. He barely noticed when the flames went out, or when he fell to the ground.
Do not hate me, Oachto of the Sun Warriors. I had to see if you feared the flame, feared death, and thus feared me. Yet you showed courage, and even through your fear, you tried to strike me down.
Oachto opened his eyes. He was before Agni once again, and Agni was again a thousand-winged dragon. But this time, Oachto could not stand, for he had been burned by Agni's flames, and he was dying.
Your people will not perish, Oachto. Their spirits burn brighter than any hearth; they will survive the flood. And you will be there to teach them my gift when it is over.
"I will?" asked Oachto, with the last of his breath. "How?"
Agni reached forward with a bright, burning claw, and placed it over Oachto's stomach. And as the sun warrior's human body seared away, Agni said:
Yes, you will.
Oachto spread his blood red wings, and roared a dragon's roar to the cloudless sky.
A/N: 'Kai' is 'meeting' in Japanese. And Agni, of course, is the Hindu god of fire.