People never wondered why the entrance to the Chamber of Secrets was in the girl’s bathroom. They knew Tom Riddle had opened it, and that it had been made by Salazar Slytherin and assumed all the Heirs of Slytherin had been male.

Of course that wasn’t the case. Salazar knew the men of his line were rash and unthinking, and recalled his mother, wise and thoughtful, who’d taught him to speak Parseltongue, how to conjugate verbs and use the past tense in a language of hisses and sibilants.

It was the women of his line who opened the Chamber first. They didn’t use it to remove Muggle-borns, they were of the belief that Muggles were to have no place in wizarding society but that anyone with magic of course deserved a place, even if educating them with true wizards was a bit much. Instead of killing Muggle-borns they killed anyone who advocated for Muggle rights, or goblin rights or for simply supporting Muggle knowledge of their world.

In 1268 Herpeta Slytherin killed the two children of a Minister who suggested helping Muggles with magic.

In 1306 Serket Shafiq, daughter of the last Slytherin to bear the name, killed four Weasleys.

In 1448 Medusa Gaunt killed a half-blood who thought to share magic with Muggles.

In 1513 Ariadne Gaunt killed three and petrified four of a group who were planning to set up a healing center for Muggles.

And so on and so on. Maia Gaunt I killed fourteen, the most of any of the Slytherin girls; Ophidia Malfoy II killed a fellow Slytherin who’d had ambitions into the muggle political sphere. Vipera Selwyn-Gaunt, the last Slytherin girl, elected to seal the Chamber of Secrets, after the Basilisk almost killed her, making it almost impossible for anyone to get in for two centuries. No one dared try to breach her enchantments.

Until Tom Riddle, stubborn and rude, pushed his way into the girls toilets and noticed the snake carved onto the tap.

Open, he said, let me in.

I must not, the metal snake replied. It is forbidden.

But I must, he said, Muggles have infiltrated our fair school. Squibs and half breeds are allowed here.

It is forbidden, the snake said with a note of finality, and spat a mouthful of water at the boy.

Tom sighed and unlooped Nagini from his neck, where she hid during the day. Talk to it, sweetling? He asked and she bobbed her head and complied.

May I enter, sister snake? Nagini asked.

You may, the snake said. But he must not. The Chamber is sealed to all wizardkind.

But he is my friend, my trusted friend, she said. He would do no harm there.

He is of wizardkind. The last Heir forbade it, the metal snake said.

But this Heir asks it, replied Nagini.

This Heir has no right to! What is said by one Heir speaks for all Heirs! The snake snapped.

Then why may I enter? If I associate with wizardkind then, by the thinking of many snakes I am as they are, Nagini said.

You greeted me as sister. You may enter and seek sanctuary. He may not.

But he is a brother to me as you are sister dear sister snake. Won’t you let him in? Nagini replied.

The little metal snake started running over the metal of the tap, confused, distraught. It had never been intended to put up with such reasoning when Salazar had placed her there. Salazar had never though such a thing might happen; divide within his own house.

Please sister snake, in Slytherins name? Nagini whispered.

Finally the metal snake nodded, and snake and Slytherin entered the chamber.

(written and submitted by the lovely essayofthoughts; once again, essayofthoughts provides us with a clear and well-written picture of Tom Riddle and Slytherin house, nuanced and fascinating, without letting up on the horrifying aspects one bit. Just how I like it.)