Harry Potter's Twin Sister

Lethrinus melanoleucos

She did it, she actually did it. After an eternity of reading through what must have been hundreds of pages on the inner workings of fungi, she finally reached the one she was looking for. Lethrinus melanoleucos.

She practically memorized the entire chapter that was devoted to this particular species of mushroom. Where is grew; what it did; how to grow it;  why it reacted a certain way; how to use it in potions; how to use potions on it. She read it all, and she never thought that she could be both fascinated by something and completely terrified of it. 

Evelyn Gray was a genius, and in to Hazel, she was a hero. Despite having been a Hogwarts professor for over twenty years, she had dedicated her life's work to finding and studying fungi from all over the world. And while Hazel didn't think that she would be able to do the same, she was definitely greatful that professor Gray had done so, because otherwise Hazel would have never discovered Lethrinus melanoleucos. If 'Everything Mushrooms' was to be believed, then this species of mushroom was exactly what she was looking for: a test subject. 

The picture in her book showed what looked like a disfigured human, rooted to the trunk of a tree. The accompanying picture was a diagram of what the mushroom looked like if you cut it in half down the middle, and there were three pages worth of information which detailed what the mushroom's reaction was meant to look like in comparison to how a human might react. For example, if wolfsbane was applied to the mushroom, then when you dissected the mushroom, a certain 'organ' should have turned green, more specifically, green A1, which was a specific shade of green along a spectrum. The darker the colour, the more effective the potion is. 

From what Hazel gathered, she would be able to tell which parts of the human body would be affected based on which parts of the mushroom changed colour, and she would be able to predict what kind of reaction the human body would have based on the colour change.

Once she had fully understood the process of testing on mushrooms, she decided that it was time to actually grow some mushrooms. This didn't require much; she had to find a damp space that got periodical sunlight; she chose one of moldiest stalls that she could find, and filled up a giant clay tray with decaying pieces of wood and plants that she had collected from the edge of the forbidden forest. The book said that Lethrinus melanoleucos grew best when there was also a blood sacrifice, but Hazel didn't feel like killing some poor bunny, so she made a small incision on the outside of her elbow, away from any nerve endings or major arteries. The blood came easy enough, and it didn't hurt as much as she thought it would. She performed a small healing spell, and soon it had formed a small scar, making it look like nothing more than a childhood memory. By the time she had cleaned up and packed away her things in a secret hole behind the framed mirrors hanging on the other side of the bathroom, it was already late into the afternoon. Hazel knew that her friends were probably all wondering where she was, but she would probably tell them that she was hanging out with Hagrid or her father or anyone really. That was the good thing about having friend groups that didn't like each other, they never communicated.

There were still some snacks and tea in the Great Hall by the time she had arrived, and it was mostly empty, save for a few friend groups here and there who hadn't wanted to brave the chilly autumn wind outside. 

Hazel entered just as a group of Slytherins and Durmstrang students were leaving, but since she was so worn out from her mushroom adventures, she hadn't been paying all that much attention. So, when she was suddenly pulled aside and ushered behind one of the entrance pillars, it took her a while to realize that standing in front of her was a very peeved off looking Draco.

"What the Hell! Where've you been?" he demanded.

"What, no hello?" she teased half-heartedly.

"I'm serious, Hazel, I've been running around this bloody castle like a headless chicken just looking for you."