In the coldest place in the world, it's the summers that are the worst.
Snows melt and tundra grass grows on the thin layer of soil above the permafrost. Mass migrations of animals return to breed, and hunting is good for a while. The sky is a deeper shade of blue, the days last longer, and children run about without their heavy outer parkas. And the once-proud city of the South Pole turns yellowish and translucent, sweating and sloughing off bit by bit.
Kya and Hakoda look at their house mistrustfully. It has begun cracking, and is probably not safe. They fear for the children. Hakoda cuts blocks of ice with his saw and props up the walls. And the child Katara runs her hands over the cracks. Kya worries at first that the heat from her hands will only speed the melting, but sees that with every pass, the crack is slightly shallower, until after a hundred, two hundred passes, the crack is sealed and Katara smiles.
They say the summers are hotter these days, and blame the Fire Nation. As it grows in power the ice melts and the ocean rises. Gran-Gran says that the Fire Nation is an island nation, and if they make the world too hot the seas will rise and drown them, just as the moon chases the sun from the sky.
The palace that lasted ninety years without waterbending is disintegrating at last. None have lived there for decades. The Fire Nation took their chieftain, their lady, their princes and princess. Hakoda leads, but he is a war commander, not a king.
Sokka and Katara explore the falling ruins. They each hold an end of a skin over their heads because of the constant drizzle inside. Sun catches in the drips, dazzling them. A family of leopard-foxes has made their den there, the new royalty of the Water Tribe. Katara looks longingly at their pelts, the sort of luxurious thing one of the real old princesses might have worn. She traces her hand over the engraved symbol of Water on the walls, but cannot force it back into cohesion. Ice is stubborn, and the thaw is unstoppable as the sea.
Gran-Gran cannot bend, but she says that she knew benders once. Katara begs her to teach her, but Gran-Gran just says that the moon and the sea are the only ones who can. She brings Katara to an ordinary-looking bit of ice, and tells her this is the heart of the South Pole, that it was a shrine once before everything melted away. She tells her that this is where she was born, on the precise axis of the world, that she is the heart of the South Pole too, and the South Pole will teach her.
Katara lies there all night on the winter solstice, the night she was born, and all the long night watches the stars go in endless circles above her. She bends a little, prays to the moon when it rises, and eventually just lies on her back, trying to take in all the sky and the ice and the sea. She doesn't remember falling asleep, but remembers waking at dawn, feeling as though she'd found something very important and forgotten it.
Bit by bit her people surrender. The palace is covered in the black snow, melted into an unrecognizable heap, and covered in winter's white shroud again. They move on, further from the South Pole proper, and mound together bits of ice and snow with their hands. Katara tries to help, but collapses as many structures as she reinforces.
Then the black snow falls again, and Hakoda leads the men away for vengeance.
Katara's mind clouds with dark thoughts. If she had been a better waterbender, she could have put an icicle right through that man's throat. She could have frozen the boats in the dock and kept her father by her side. She could at least build a better watchtower than the lump Sokka made, and perhaps save all their lives when the Fire Nation comes again.
Gran-Gran takes her by the sea and tells her to feel the ebb and flow, the push and the pull. Katara stands there until the sun sets and pulls at the sea all night, imagining her father's boat at the other end of each wave, imagining pulling him home. She pulls the sea so hard it rises above her and swallows her up, and unable to bend it back fast enough, Katara must paddle hard or drown.
Katara listens, and the sea teaches. Push it, and it will rise higher. Pull it, and it will draw further away. Every action with its reaction. Water boiled returns with the rain. She doesn't know the forms, but she lets her body be pulled into the flow.
That she will get revenge for her mother is never in question. The cycle of revenge is unending, perfect. Katara does not seek to break it any more than she would seek to break the waxing and waning of the moon. She has hated and will be hated, has lost and will take, has fallen and will rise. She listens to the sea, the source of all life and a killer without remorse. She says, "Make me strong," and knows it must because she is so weak.
Having been pushed, Katara pulls.