Salazar Slytherin's Scriptorium

"So," said Oleandra. "How did you find out about this so-called Slytherin's Scriptorium, anyways?"

The small group wandered throughout the castle's dungeon, searching for a hidden room that might or might not exist. Draco had insisted on heading there straight away, excited at the prospect of finding a clue that might help him identify the Heir of Slytherin. 

"It's a story I heard from one of our subordinate families," Pansy explained. "The Sallows. One of their ancestors attended Hogwarts about two hundred years ago and befriended a member of the Gaunt family. Together, they found and explored Salazar Slytherin's Scriptorium."

"Two hundred years ago?" frowned Daphne. "How did you come to learn this story?"

"It's sad really," Pansy sniggered. "It was the Sallows' crowning achievement, and they've been holding on to it ever since. They'll tell it to anyone who'll listen. They haven't really done anything of note, heh. Oh, we're here."

They had reached a corridor that bent at a right angle. Oleandra and Daphne looked around. There was nothing of note here except three pillars, an unlit brazier atop each of them.

"You just need to light a fire on top of each of the pillars, and the entrance will reveal itself," said Pansy lazily.

Draco and the twins stared at her with wide eyes.

"That's it?" asked Draco incredulously. "Light three fires, that seems… incredibly arbitrary."

"Not to mention stupid," said Oleandra. "What if someone decides it's too dark in here and lights them up? Then the whole secret hideout thing falls apart."

"Oh, you'll understand once we're in," said Pansy, shrugging her shoulders.

The three others each picked a pillar and stood in front of it.

"On my signal," said Draco. "Three — Two — One —"

"Incendio!" the three shouted.

With a burst of magical sparks, three fires roared to life. At the same time, the sound of stone grinding against stone was heard. As Oleandra turned around, she witnessed part of the wall sliding back, revealing an opening. She approached the entrance and peeked inside. A spiral staircase descended into the murky depths.

"Well, that was easy," said Oleandra, scratching her head.

The small group descended the staircase, wands lit to keep the darkness at bay. They were soon forced to stop, as their path forward was blocked. A great metal door stood in their way, embellished with reliefs of snakes. Oleandra shone her light on the door; the great mass of metal snakes seemed almost alive, in a way. And was it just her imagination, or could she hear snakes hissing?

"There doesn't seem to be any way to open this door," observed Daphne.

"You need to be a Parselmouth to get it to open," explained Pansy. "Now unless one of you can speak Parseltongue, shall we be on our way?"

They all looked at each other. None of them could speak to snakes, it seemed. Draco tried some hissing, but the snakes on the door bristled with anger, making the group back away. It seemed like trying to hiss like a snake was the equivalent of making exaggerated hand movements at an Italian; in short, it was pretty racist, and they didn't like it very much.

Pansy didn't want to stay here any longer than she had to. 

"Come, Draco," she said to him soothingly. "Let's leave those two and get back to our conversation, shall we? They can tell you later if they somehow manage to find a Parselmouth."

She pulled at Draco's arm, and he reluctantly left with her, leaving the Greengrass twins alone in front of the door.

"Got any ideas, sister?" asked Daphne, once the other two were out of earshot. "Hogwarts's walls are enchanted to resist damage, and I have no doubt Slytherin's added even more defences to his Scriptorium.

"Do you remember when we fought against the giant three-headed dog?" asked Oleandra.

"How could I forget?" Daphne rolled her eyes. "It was quite gruesome, indeed."

"My trees, they pierced through the ceiling," Oleandra specified. "Nature always finds a way, right? That's the Greengrass family motto. Mighty oaks may be felled, but the humble weed will always endure."

Oleandra waved in the direction of the door.

"Look at all these snakes. They do make the door look cool, but all I can see are structural weaknesses. Do you see what I mean?"

"I think I do, dear Sister," Daphne grinned. "Shall we get to work?"

Oleandra and Daphne gingerly approached the door; seeing it wouldn't launch any attacks, they placed acorns wherever they could on it. It was pretty dark in this room, the door was sure to be enchanted to resist attacks, so Oleandra would have to alter her tree growing spell a little.

"We'll add Sowelo; the sun rune, Yera; the Year rune and Dagaz; the time rune, the sideways hourglass, but right side up," she said, thinking. "This way the trees will have the sunlight they need, and time will accelerate instead of stopping, ageing the door and speeding up the trees' growth."

Oleandra had previously used the Year rune to fix a potion brewing mistake, for the passing of the year rune also held the meaning of bountiful harvest (after a year of cultivation).

A moment later, they had the incantation ready; it was showtime!

"Sowelo, Berkana, Fehu, Year, Dagaz!" they chanted, as they danced, limbs forming the shapes of the runes. "Let the sun shine on the Dark Lands, let our seeds beget a world of trees, and may time wither our enemies!"

They were pretty deep underground, so they had a moment to run for cover before the magic of the stars reached this far down. And then…

BANG!

Oleandra's vision was suddenly filled with greenery. In the ceiling floated a small sun, emitting a glaringly bright light, which filtered through the leaves, bathing the room in a gentle emerald green light. Shards of metal lied scattered at her feet; the small metal snake heads seemed to be looking at her accusingly.

A bead of sweat rolled down her face. They had been lucky; they could have been impaled by a stray branch, or hit by door shards.

"All yours, Sis," said Oleandra, pretending they hadn't almost got themselves killed by their own spell.

Daphne drew her wand; a few waves later, a wooden door had taken shape in the twisting mass of tree trunks. She grabbed its doorknob and opened it.

"After you, Sister."

Oleandra took a deep breath and stepped inside. She took a moment to admire her sister's handiwork; a tunnel had been perfectly formed through the wood, its walls felt cool and smooth to the touch as she ran her hand along its side. 

Then, she moved further in. A few seconds later, the sisters had made it to the other end of the tunnel, they were finally here!