Anon, you are beautiful for sending me this and let me just say, I love your face. Now this is why I do need to write my own meta on the subject – and since you came by, Im going to do it right here.
Starting from the top – as much as I love Severus, I know he would absolutely have told anyone who could listen ( NOT TO MENTION HIS FUCKING MOM ) that Remus was a werewolf had his mouth not been all but literally sewn shut. Remus was part of a pack of bullies making his life hell, and it wouldn’t be a matter of long term thinking, it would have been short term viciousness and vindication followed by long term guilt as he grew older.
Now on my blog I write this attack as having taken place in Severus third year, despite the canon evidence of it occurring in the sixth. While all of my reasons for that are in the POA portion of AID, regardless of the time frame in the event I AU my own Severus to RP with someone who dearly needs this attack to occur in sixth year, he would have babbled. All the live long day.
Now as it happens, he was sworn not to. Which put my dear Severus in a pickle when one of his friends (who comes from a family of werewolf hunters) figured it out on their own based on obvious signs Remus presented. Which is where stipulation comes into play:
Severus could not speak of Remus’ condition to anyone save those who were already aware which meant that even if Remus was going around unchecked, his hands would be tied beyond screaming at Albus. As it was, Severus (in my canon this is very divergent right here) was placed in a unique position of choosing life or death for Remus Lupin, and it is for this reason that Remus is so clean slated in Severus’ books. He had to be, to justify what Severus did next; he swore his friend not to harm Remus.
THIS WAS NOT DONE BECAUSE SEVERUS WAS A GOOD & FORGIVING TEENAGER. It was done because he didn’t want something bad to happen to his friend and more so because he didn’t want to be anything like Sirius Black. He didn’t want to weaponize someone he cared about. This wasn’t altruistic; Lucas at this point was Severus’ biggest shield and protector. Severus needed him and while there’s seeds of good reasons, ultimately even this was self serving.
However, Lucas had his own stipulation that Severus prove he could defend himself from a werewolf before he agreed not to actively hunt Remus down. This, is what lead to Severus creating sectumsempra in his fourth year, though it was written in his sixth year textbook for a friend he was sharing said textbook with. It is a good thing Severus is a weaver, or this would have been hard for him to accomplish at this age.
AS FOR HIM TELLING IN HARRY’S THIRD YEAR:
As Sky covered, he actually didn’t. While Sky did not provide reasoning beyond divergence, MY DIVERGENT ASS HAS REASONING, mainly because this is something I’ve written with Remus players in the past and its one of my favorite things.
Because you cannot tell me Severus singlehandedly destroyed Remus Lupin’s life, and that of all werewolves ever, and was like hoho but Dumbledore trusts him so clearly he is above all suspicion and you’re just being biased Harry, because if you think Remus doesn’t have his own mean streak you need to rethink his choice in friends. Remus is great and I love him, but nobody is that forgiving, or that stupid, and Remus is a lot of things, but if you want to tell me he is stupid you can gtfo.
It is canon on my blogs that Albus helps Severus perpetuate his Dark Reputation. I dont think this is a stretch considering what canon material offered us in Severus begging him to hide the good in him. Albus perpetuates rumors via Hagrid and portraits and school ghosts. All of whom either think it good fun or believe him wholeheartedly.
In my rendition of matters, Albus let Remus go because he forgot his potion and that is a serious endangerment of children when he had no restraints in place, either. The JOB IS CURSED, HE HAD NO CHOICE BUT TO LET LUPIN GO. However – you can’t tell me Albus didn’t explain the situation for what it was, or that he didn’t encourage Remus to ensure Harry and the others believed it was Snape spreading the rumor, though Albus would likely claim he ‘did not know the true source, as so many students have been taught the signs’ it would, essentially, be tied to default to Snape but not overtly be his fault in Remus’ eyes – thus affording Remus his forgiveness abilities, Albus further fuel to fan Severus’ dark flames without spreading too much damage, and Severus the continuity of his oaths not to speak.
AS FOR THE FALLOUT OF UMBRIDGE WRITING UP WEREWOLF LAWS: There’s no way Dubledore saw that shit coming, first of all, because he did make efforts to contain the information and how far it spread. Hagrid telling the odd youth who asked why he was gone, making Severus’ assignment seem at fault, was meant, I imagine, to keep things relatively in check as with Remus gone, it was not a standing issue. But it did become one, which I imagine he regrets.
I know for a fact, Severus does. However, teaching children to identify werewolves with a werewolf on the loose was not breaking his silence. He did not tell them there was a werewolf in the castle, only how to look out for one. And considering his last encounter with Remus was nearly deadly, I cannot fault him for educating them about the risks of werewolves when there’s one in the castle – because as much as I love Remus, that shit is important to know and yes, Severus is petty, and he has a harshness to him and even a cruelty at times.
But he does not regret making certain every child in that school could protect themselves if something went wrong, which it very nearly did.Because at the end of the day, hate his job though he might, my Severus will always prioritize the safety of his students first and foremost, and he doesnt give a damn if that means sacrificing things like happiness or another mans pride.
I cover Severus and his relation to his students in a lot of my headcanons, but this one and this one are most relevant here.
Thank you again for this question! Hope this covers everything xD