The thing about Peter Pettigrew is that from an outside perspective, he was just a follower. Always riding at the tails of the other three, willing to be cuddled and cooed over by James, taking advantage of Sirius strength, and allowing Remus to fuss over his notes.
So, really, it wasn’t Professor Riddle’s fault he misread his place in the Marauders.
Especially when Peter had doubled down on the mask after their first encounter; the others had found it amusing, a dare they could get to enjoy. Peter hadn't. He took a look at the man and immediately put him at the top of his threats-to-deal-with list.
Thus, Peter ensures Professor Riddle only sees kind, cowardly, dumb Peter.
Of course, he can’t take all the credit here. If the others had not gone along with it, things would have ended very differently but Remus caught up with ease and Sirius has always been too good at turning annoyment into hate— James is a little slow, trying to defend his honor as Professor Riddle tries to bash his lack of usefulness in their last prank.
He almost drowns for his troubles, too.
James barely manages to keep him afloat after Tommy lands him on the Black Lake, during winter months, for a second time that night. And Peter vows vengeance on Dumbledore for allowing a maniac like Professor Riddle to teach children as he gasps for air and curses Sirius inside his mind for pointing his weak spot for James out for everyone to pick it up.
The next few months are not fun.
He spends his time alone. Out the common room before the others, returning when he’s sure they’re asleep. He stays at the sidelines, watching his friends hogger the attention of the terrifying wizard and allowing him time trying to find -on his own, I may add- the best way to get rid of the bastard.
He only joins them when it’s full moon and Moony tries to eat him, showing his displeasure, so Wormtail takes to sitting on Prongs’ antlers instead of running between their legs and biting toes and tails as he usually did.
Then, something shifts.
He doesn’t know what happened. But something did. And whatever it was turned his friends into a frenzied mess; Sirius uses the mirrors for the first time since Professor Riddle arrived at the castle, contacting him with puddy eyes and trembling limbs.
He only says one word to him before hanging up: Wormtail.
It was a call to action. A plea. Peter seethes under the candlelight, vision turning red, because Sirirus was the strongest of the group, he was larger than life, and there shouldn’t be anything that made him look so scared.
(Not even Walburga Black, because the woman didn’t scare Sirius. Not really. Not now when she couldn’t touch him anymore.)
Peter went to Regulus, the new apparent heir of the Ancient House of Black, pointed his wand at him, and whispered Imperio.
Gaining access to the Black Library does make things easier— So many delightful rituals there. He needs to get back here in the future, there is much he wants to try.
But first things first, dealing with Professor Riddle is the top priority.
It takes him another two weeks to lay the ground for the ritual, careful to not tip Professor Riddle, taking the snakes out first, and then engraving the runes on the stone floors with his own claws, breaking the spell in four so there’s no way he will know for sure what it is even if he does find the marks.
By the time he’s done, the other three had already changed the wards of the entire castle and Peter is a little put out from not being able to help with that, but he is having fun on his own, anyway.
So really, he can’t blame them for doing the same now, can he?
Tom Marvollo Riddle, half-blood, Bastard of the Gaunts, sleeps with more peace than any Dark Wizard deserves but Peter bets because he’s so secure on his own power to lose sleep.
It’s kind of annoying, even if it’s useful.
Black rituals always ask for a price, the more cruel the ritual, the more grotesque the sacrifice that needs to be made. In this case, Peter has to gouge his own eye and then shove it down Tommy’s throat and ensure he eats it.
By the time he’s done, no amount of tergeo or scourgify will be enough to make the room slightly habitable. The blood will not come out and neither will the ashy impression of body parts.
Peter is missing three fingers, one ear, his eye, and a chunk of his right side. Nothing Madam Promfy has tried until now has worked and Peter thinks nothing will, he was injured by dark magic. And if he’s being honest, that he’s alive is a miracle.
A miracle called Sirius Black, Remus Lupin, and James Potter.
No one is really surprised they managed to pull it. If anything, the thing with the barriers is more impressive. Because they had just mauled their souls and exchanged tiny bits of it, merging their lives and health.
Not that they mind. Not after this experience; being separated is no longer something they want to contemplate. No, they’ve reaffirmed what they’ve discovered during their first year at Hogwarts: The Marauders belong together.
On the lighter side, though, is that they will not be bored anymore. It turns out that planning to ruin a man’s life and career is a great way to pass the time; Dumbledore has proved to be as amusing as Professor Riddle if in entirely different ways.