It starts when Ron Weasley meets Harry Potter on the Hogwarts Express and thinks, huh, he’s nothing special. And that pleases him, in a twisted sort of way.
No, no. Let’s back up a bit. It might have started before that.
It might have started when Ron turned eleven and was gifted Percy’s old rat. It’s not the first time he’s been handed something that belonged to someone else, but it’s definitely the first time that thing is a living, breathing being. So he takes care of Scabbers, and confides in him. He loves this rat, even if it’s old and useless. He tells him he wants to be special, more than another Weasley. He tells him he wants to have his own things, and live in a house he’s not ashamed of. Scabbers’ whiskers only twitch in response but somehow it feels like he understands.
(And he does, because Scabbers is Peter deep down, who trailed after James Potter and Sirius Black, two heirs of prestigious Houses who threw money around like it was nothing while Peter had to get a summer job to pay part of his Hogwarts tuition.)
It might have started with the squib cousin they never talk about too, or sitting on Aunt Muriel’s knee while she forgot herself and ranted about Grindelwald being such a handsome man. It might have started with his father’s fascination with muggles but his complete inability to interact with them. Ron grows up prejudiced, but his ignorance is smothered under the ostensible goodness his family projects. Dumbledore likes them, people say. They must be a good sort.
It might have started in little things during his first two years at Hogwarts. The second it took him to agree when Harry and Hermione cried about injustice. The frown he smothered when Harry told him about freeing a house elf. The resentment that built when his best friend was so bloody mindful of his financial situation.
He’d always remembered the bewilderment on Harry’s face when he’d told him what he saw in the Mirror of Erised. Because how could any dream of his compare to seeing his dead parents?
It definitely started when Peter Pettigrew pleaded for his mercy. Ron felt disgust at being duped, sure, but also frustration. Scabbers was his, why did he have to be taken from him?
So it festered like a wound nobody could see until Harry’s name came out of the Goblet. Then it all came out. The jealousy, the frustration. He’d felt duped again. Scabbers hadn’t been a rat, after all, maybe Harry had always wanted the fame he pretended to deny.
And he was left alone with his rage, to stew on it. Sure, Hermione spent time with him, but she’d been obsessed with her house elf campaign and it was so bloody ridiculous spending time with her alone wasn’t exactly a reward. So he’d been mostly left to his own devices, save for a few interactions here and there. He’d taken to walking down the corridors, overthinking. One day, he’d met professor Moody, who’d taken him to his office. The man had talked about him, and only him. Not about Harry bloody Potter or his brothers. He hadn’t even mentioned his father again, who’d helped him out in the summer. It had been only him. So Ron had come back, even after reconciling with Harry.
And the thing is, Ron wasn’t that smart, but he noticed patterns. Like the exact frequency at which the professor drank from his flask. And the smell he’d deemed familiar, but which he couldn’t pinpoint. Until one day, it clicked. He hadn’t said anything, though. He’d lost Scabbers to that big reveal at the end of third year, surely he could enjoy not-Moody’s attention on him a while longer?
Not-Moody had noticed though. He’d locked the door with him in it, and waited. The polyjuice faded and revealed a blond man with a manic gleam in his eyes, who kept licking his lips and had cackled when he’d seen that Ron hadn’t twitched. He’d asked why Ron hadn’t said anything. He’d stumbled through an explanation and the death eater had looked… sympathetic. And he’d told him how he met You-Know-Who. His father’s anger, his mother’s neglect. The feeling of being forgotten, until He’d come to him. He’d given him His undivided attention, interested by his talents, and Barty -because he was Barty Crouch’s son, the same who had turned up dead a few days before- had revelled in it. Then he talked about their goals. Their ideology. And Ron… got it. Not all of it, of course, but he got the feeling that purebloods were being overlooked, their way of life changed by the incessant demands of muggle-borns who couldn’t accept that things were just the way they were and everything had worked out fine before, they didn’t need to dismantle a system that was fine.
He’d told Barty exactly that, and the man had seemed delighted. He’d told him about how normal Harry was, how unfair it was that he had so much attention on him when he wasn’t anything special or grand, or deserving of that fame. They kept talking, and Ron felt galvanised. He had a confident again, one that talked back this time and didn’t judge his resentment, his envy, his anger at how unfair it all was.
And then Barty had been Kissed. Ron once again lost something that was his. So he sneaked out and sought out the Dark Lord Barty had loved so much. He'd been hesitant at first, and guilty, but the Dark Lord had assuaged his reticence. He'd welcomed him whole-heartedly.
Maybe that’s how it really started. Soon, Ron was giving out secrets. While the family called Percy a traitor for following the Ministry, there was a worse rat in their midst. Harry’s fears, his attachments, his deepest thoughts, he shared it all. He got so good at lying to his friends and family it felt like he was only telling the truth in front of his Lord. Sirius died and Ron felt nothing at Harry’s distress. He was just restless. He hadn’t been a useful spy yet, and his Lord was getting impatient. But then, then Harry told him about the prophecy and the Horcruxes. There was his chance.
That day, Ron had his first taste of the Cruciatus Curse. But he was thanked right after. Draco Malfoy took too long to repair his vanishing cabinet, so Ron suggested the Honeydukes entrance and borrowed Harry's map and cloak to facilitate their entrance. The death eaters invaded Hogwarts on Halloween night, as a fuck you to fate.
A week before, Ron was branded by his Lord. On the day of the invasion, he bore the Dark Mark with pride as he turned on his classmates. And he smiled as Dumbledore fell off the Astronomy Tower, right after Harry Potter.
Ron Weasley wanted to be something no one in his family had ever been, so he became a traitor. And when Lord Voldemort ruled on a pile of ashes, he was right by his side.
And if Pettigrew had been turned back permanently into a rat, well. Scabbers had been such a wonderful companion, it was only natural his Lord would want to give him back to Ron as a reward to his loyalty.