Stupidity is Contagious

Dark magic exacted a certain toll, Oleandra had always known this. Just as the Sigil of the Helm of Terror allowed her to absorb others' fear and turn it into her own power, so did it magnify her own fears. If she overused its magic, Oleandra feared that one day she'd be scared of her own shadow. This wasn't the sort of person Oleandra wanted to become, so she once again resolved never to use dark magic unless she absolutely had to.

To take her mind off things, she went to see Slytherin's next Quidditch match. This time around, they were facing off against Ravenclaw. Oleandra rarely had the chance to interact with Ravenclaw and Hufflepuff students, so she didn't know any of the Ravenclaw Quidditch team members.

Well, she knew one of their names, actually. As an ex-Seeker, Oleandra was only mildly interested in other Seekers, so she knew their Seeker was an Asian girl named Cho Chang.

At any rate, Slytherin managed to completely flatten Ravenclaw. Marcus Flint, the Slytherin team captain, had heard from Draco that Oleandra was a master Runesmith, so he had the entire team's Nimbus 2001s engraved with Raidhu, the riding rune. And the difference was immediately noticeable; Ravenclaw never even had a ghost of chance of winning!

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With her mind off things, Oleandra returned to the humdrum life of an ordinary Hogwarts student; it was nice taking a break from fighting and adventuring, sometimes. Despite the setback both Oleandra and Harry had experienced on their first Patronus lesson after winter break, they still kept returning week after week.

Luckily for Harry, he had plenty of experience casting the Patronus Charm at nothing, so his progress wasn't so bad. It was already an incredible achievement for a thirteen-year-old to cast an Incorporeal Patronus, or so Professor Lupin had told him. And indeed it was; he had stopped fainting when facing the fake Dementor, and he could somewhat repel it with his tornado of silvery light.

As for Oleandra, in order to get some practice in, she had to hide behind Harry in order to take the Boggart by surprise, to stop it from shapeshifting long enough for her to cast her own Patronus at it.

And that is how Oleandra spent her days: going to classes, studying with her sister in the common room and practising with Harry and Professor Lupin. Sometimes, she'd look at the Daphne's piles of homework and see if she could understand any of it (she couldn't, not even if she used Ingwaz, the divine spark rune, which couldn't invent information out of nothing).

Recently, Oleandra noticed that her sister had taken to spending more and more time with Hermione in the library. It was natural that they'd study together, as they were both taking all the classes that Hogwarts had to offer. But still, the other Slytherins didn't know this, and they had no problems gossiping about the Greengrass family's poor choice of friends.

From what Oleandra understood, the Gryffindor Trio were fighting again, because Hermione's cat had eaten Ron's pet rat, and Hermione felt as if Harry had unfairly taken Ron's side, because there was no definite proof that the cat had eaten the rat. This was apparently why Hermione seemed to spend so much time with Daphne: her other friends had effectively ditched her. 

Oleandra had pretty much given up on trying to talk to her sister when Hermione was around; all they did was talk about their Arithmancy homework. And on one such day, when Hermione and Daphne seemed stuck together at the hip, Draco, along with a few Slytherin Quidditch team members, came up to Oleandra in the common room. 

She'd been busy lazing about, trying to find excuses not to get started on her History of Magic homework. And behold: an excuse appeared before her eyes.

"Are you coming to the match, tomorrow?" Draco asked her. "Gryffindor versus Ravenclaw."

"Well, I dunno," Oleandra said, looking at her fingernails. "I've got a lot of homework saved up. Maybe?"1

"We were planning on playing a little prank on Potter," Draco said. "We'll disguise ourselves as Dementors, to throw him off his game. If we're lucky, he might even fall again and break his neck."

"Now, this I've got to see," Oleandra said, raising an eyebrow, "But what do I have to do with that?"

"You could help us," Marcus Flint said. "You could stand on Crabbe's shoulders, he's a bit too short to pass for a Dementor."

"I'm going to have to say no," said Oleandra. "But now I'll definitely be going to see the match, so yes, I'll be rooting for you in the stands."

"That's too bad," said Draco with a disappointed look on his face.

"Oh, and by the way," Oleandra added as they were leaving. "You might want to look out for Potter's Patronus Charm. He's been learning it as well, so don't be too surprised, 'kay?"

"It's that white, silvery thing you did at Christmas, right?" Draco confirmed. "All right, we'll keep that in mind. See you tomorrow."

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"I've never seen you this excited for a Quidditch match before, Sister," Daphne said as they all sat in their seats in the Slytherin bleachers. "This isn't even a Slytherin match. Something I need to know?"

"Do you need an excuse to be excited for Quidditch?" Tracey retorted. "Although, the odds are against Ravenclaw. Gryffindor's seeker, Harry Potter, has a near-perfect record of catching the Snitch. He's on a Nimbus 2000, which despite its tendency to list slightly to the left, is far superior to his opponent Cho Chang's Comet 260."

Oleandra didn't dignify the sports nerd with an answer. The match had already begun, but she was too busy looking out for the moment where Draco would make a fool of himself to focus on the game. Harry didn't even faint to the Boggart now, so there was no chance in Hel that Draco would be making Harry fall off his broom.