au where sokka, not their mother, is the one who sacrifices himself for katara (inspired by this post about sokka looking like his mom)
Sokka and katara are together in their house when the southern raiders attack
Their parents are out when the soldier yon rha breaks into their home
He knows that the north only trains boys in waterbending… he thinks the south is the same way
The kids are cornered by yon rha, who tells them
“I won’t hurt you kids if you tell me who in your village is the last waterbender”
Katara is terrified and knows he’s come for her
Sokka looks at his sister and thinks it’s up to me to protect her
So he says “it’s me. I’m the last waterbender of the southern tribe.”
Yon rha was planning to kill the last waterbender, but it’s only a child… he decides to kidnap sokka instead
Katara watches as her brother is dragged away, unable to stop the man as he takes sokka from her
All that’s left of sokka is his beloved boomerang
Yon rha takes sokka to a fire nation prison far inland in the earth kingdom colonies, even though he’s the only child there. Without a master or water around, he reasons, sokka is no threat.
Katara still has both parents, but she’s lost her brother and best friend and feels that it’s her fault
Sokka grows up in prison, learning how to fight when he’s smaller and weaker but cleverer than his fellow prisoners
As the only child in the prison, sokka has to play up his role as a harmless and agreeable kid. He’s funny and the other prisoners derive amusement from it, which means they’ll keep him around
He never forgets his water tribe roots though, or his family
Katara grows up lonely and determined, learning to hunt with the boomerang and a spear and waterbending all together. She’s not the caretaker role now, but the angry rebel daughter, brave but rash and proud and desperate to prove herself
One day she’s out hunting alone when she discovers a very special iceberg. Curious, she breaks it open immediately (bc let’s be real sokka is 95% of her impulse control in canon)
When sokka is fifteen, he successfully escapes from prison and makes his way west to the coast
He gets ambushed in the forest one day, and almost gets killed by a boy with hooked swords who accuses him of being fire nation (his prison shirt is red)
Sokka argues “no! I’m water tribe!” jet doesn’t believe it at first, but the blue of his eyes doesn’t lie
Jet is impressed by sokka’s fighting-dirty style and great aim and invites him to stay
Sokka joins the freedom fighters but is disgusted when he learns about jet’s distorted sense of justice. He starts planning a way to overthrow jet from the inside
Meanwhile, katara and aang travel north to find a waterbending master, and they just so happen to run into jet while flying over a forest
When they get to the treehouses, they run into a skinny, scrappy dark-skinned boy whose jaw drops when he sees katara
She doesn’t recognize him at first, and then all at once she does
“SOKKA?” “Katara, is that really you?”
There’s much crying and hugging and “how are you here?”
Sokka explains his plan to katara and aang, and they know not to trust jet
Jet’s plan is foiled by sokka and gaoling is never flooded
Katara gives sokka back his boomerang (“You kept it all this time?” “Of course. I’m probably better at it than you are, now.” “No way!!”)
They fly north. Katara has to relearn her brother, relearn his mannerisms and his personality. She’s surprised by how little he’s changed, even though he’s been through so much
Sokka is a harder version of himself, sharper and more cautious. But he still has his sense of humor and his clever plans, his same hairstyle and bright blue eyes.