A little story about the sweaters Petunia knits throughout the years for her enemy. Merry New Year.
At six years old, Severus had received his first sweater at a school Christmas party. It was anonymously put on his desk, and when he'd opened the package to reveal the lime green sweater, he'd thought it was the most wonderful thing. He'd put in on in amazement and pride, but everyone laughed at him.
He'd gone home in tears by lunch to find his father at home, strangely enough. His father had taught him a lesson that day: Never, ever let them see you cry. "Get angry, taunt back, or show off your brains with wit and sarcasm," he had said. "But don't ever let them know they've gotten to you and hurt you. Never cry." Severus took this lesson to heart. But he never wore the sweater again.
When he was seven, the sweater was a grayish-orange. When a bigger boy teased him about it, Severus accidentally on purpose set the coat that he had reached for on fire. The teacher put it out by grabbing it and stomping on it, and the bigger boy was suspended.
When Severus told the story to his parents later that night, Eileen had to explain to both of them about magic, both accidental and purposeful. That was the night Severus learned about Hogwarts, and the night his father started drinking.
For his ninth birthday, Petunia sent him a striped sweater comprised of stop-sign red and construction-orange. There was also a note telling him to stay away from her sister. He, of course, paid no heed.
The sweater came in handy that year, since he spent most of his days outdoors, staying away from his parents, who were becoming increasingly less compatible with each other. The days that weren't filled with shouting were often silent, tension-filled glare fests, and Severus would really rather not participate in any of it.
For his eleventh, Severus received a green and white sweater, and he'd sent Petunia a thank-you note. She'd written something very scathing back to him, but he could tell she was pleased.
At his second-year Christmas, he stayed up to see if Santa was real. When an ugly house-elf appeared in the room, Severus woke the House up with his screams. After a rather grumpy Malfoy explained to him what exactly a house-elf was, the House collectively ignored him for the rest of the day. Because of this, Severus not only wrote a nice thank-you note, but a summary of what happened. Petunia sent back some sarcastic remarks and laughter.
Petunia sent a blood-red sweater with the words, "Lion Bait" knitted onto the front for his thirteenth birthday. That was the year Severus realized that Lily actually wrote to her sister frequently. He knew she complained that Petunia never wrote to her, but he'd never put two-and-two together.
By his fourteenth Christmas, Severus was skilled enough to make Petunia a magical watch. Aside from telling the hour, minute, and second of the day, the three hands could also tell Petunia how her mom, dad, and sister were. There were twelve settings, home, work, sick, happy, sad, hurt, mad, school, trouble, danger, nervous, and dead. In return, Petunia sent him an ugly yellow sweater and no note. The other Slytherins advised him against even putting it on, but he did, just to be boneheaded, and to everyone's surprise, it actually looked rather nice on him, which was Petunia's note in itself. For the rest of the year, however, Severus was frequently jibed about looking like a Hufflepuff.
Year five, Severus didn't wear his sweater. The other Slytherins noticed, and asked about it. Petunia had knitted it out of red and yellow as a joke. The Slytherins had to agree that it was funny, and then asked whether the knitter was his girlfriend or his mother. "Neither," Severus had replied. "She's an old enemy." The Slytherins, of course, didn't believe it. No one gave their enemies presents, year after year.
Years six and seven Severus didn't receive any sweaters. The first time it was because Petunia was mad at him for ending his friendship with Lily the way he did and making her suffer that summer. The second one was because her parents had been killed by Death Eaters, and she blamed him. Severus understood, even if he thought it was an unfair accusation.
He didn't receive another sweater until he was twenty-four, though he did get several letters from Petunia, sometimes full of hate and blame, others just noting the dullness of not having a magical sister around. Sometimes she just wrote to affirm that there really was a magical world.
Once Severus was about twenty-seven, her letters changed to tell of what Harry had done now, how Vernon always punished him, even though he had no idea what he'd done, and how she knew it was utterly foolish to try and discourage the magic in Harry, but she knew she couldn't stop Vernon. They also became less frequent, once more coming only at Christmas.
When Severus was thirty-five, he started writing to her as a correspondent instead of just thank you notes. He sent her article clippings and news of what was happening in the Wizarding world. He informed her of what he could, mostly so that he could put his role in the war into perspective. So that he didn't forget that it had a bigger purpose than the misery he was put through on both sides. He got snappier in class and more polite in his letters and the thing he most looked forward to that year was Christmas, because there was always a slight pause on both sides while the minions celebrated and the masterminds reevaluated their chess strategy.
In the summer of '97, Severus warned Petunia of what Harry was about to do, and what it would likely amount to. He notified her that she would almost certainly be put under the Order's protection. While she was, she had plenty of time to knit sweaters. She knitted sweaters for every magical person she knew, plus Squibs, and Muggles who were close.
Severus never got to wear Petunia's last sweater. It was black, with a large red heart covering the front.