1. Pre-Hogwarts history
Avalon Morgane Sylvester, who prefers to simply be called 'Ava', was born on December 21st 2006. She is a pure-blood witch of the well-known Sylvester family that moved to France in the 12th century after one of their kin committed a serious crime.  Ava's father was the first of the family to return to the United Kingdom, where he married and stayed. He built a house for his family up in Scotland, where Ava was born.

The Sylvester family is well-known for their natural skill in wandless magic, which is often triggered by heightened emotions and can put others in jeopardy. Because of this, Avalon was homeschooled by her parents in order to avoid any accidents. This was also done because they did not want to send her to a Muggle school, since they were proud to say that they were perfectly anti-Muggle, thank you very much. Avalon's youth was therefore very isolated, only being kept company by the books on the wizarding world her parents brought home from Diagon Alley, and the old house-elf Ichabod. Avalon herself was not yet allowed to go with them to Diagon Alley, for reasons she would only later find out when finally going there for the first time in her life to get her supplies for her first year at Hogwarts.

Diagon Alley

When Avalon got her letter, she was ecstatic. She would finally be able to go to Hogwarts and learn magic, something she had only ever read about! However, her parents still would not let her, and again did not explain why not. Avalon was livid and stormed upstairs, where she called for their house-elf Ichabod. "Take me to Diagon Alley," she pleaded, holding back tears. "Just this once I want to see it for myself." 
Ichabod, who cares for Avalon very much, complied and transported her to Diagon Alley. Here, she finally realised what her parents had been trying to protect her from. People looked at her funny, and she could hear them whisper around her. "That's a Sylvester, right? What's it doing walking around freely? Isn't she dangerous?" 
Met with such blatant antipathy, Avalon quickly understood her role in the wizarding world: someone to fear, someone who would grow up to do horrible things. 

Her parents quickly found out that she was gone and went to pick her up. They told her the reason for everybody's fear: the Sylvester's were Gellert Grindelwald's staunchest allies, and were known for indiscriminately slaughering his enemies and innocent Muggles for the greater good. The Sylvesters are great at wandless magic after all, and can hone their skills to harm or kill others. They told her that she would probably face discrimination at school, and it would be in her best interest to get in the Slytherin house, since they would show her the respect she deserved.

Anecdote from her past
For her seventh birthday, Ava received a book on magical creatures. Here she read about Nifflers, and was so enamoured by Nifflers that she begged their house-elf Ichabod to get her one. He did, and came back with one that managed to ransack the abode in ten minutes. Naturally, Ava's parents were less than happy, and Ava spent the rest of her birthday putting everything the creature had collected back in its place. Her parents, realising her newfound love for creatures, got her a Kneazle as a belated birthday present, and made her promise to never bring other creatures in the house again without them knowing it.

Roommates: Paws Greenan, Crystal Willows, Jane Dandrige, Edith Woods

Eris Elcan - met her at Madam Malkin's and on the Hogwarts Express, a good acquaintance

Adam Harringtom - met him at Madam Malkin's and on the Hogwarts Express, a good acquaintance

Avalon's story in chronological order

Avalon purchases her wand.

Avalon travels to Hogwarts, meeting some other students. 

Ava purchases her school robes and meets some other first-years.

The Sorting Ceremony

Avalon finally arrives at Hogwarts and is ready to be sorted. 

Discovering the Common Room

Avalon sets foot in the Common Room for the first time. 

Dorm 14

Ava grew up very isolated. Her parents are both very anti-muggle, so she shares their sentiment. She can accept muggleborns only if they are members of the Slytherin house, since she believes that Slytherins should support each other as all other houses seem to be against them. 

Ava likes keeping everyone a friend, or at least likes making everyone feel like she is on their side  She acts nice to pupils from other houses, unless she has a real reason to openly show her disdain for them. She does not promise anyone but her close friends her loyalty and never truly makes her intentions known, not often saying what she's thinking directly.

Ava is a very reserved person, and keeps her emotions and motivation hidden as much as she can, but she has limits as well. Ava is sometimes easily provoked, which is dangerous because she easily resorts to her wandless magic.

Ava likes people who have a particular talent, are from a pure-blood family, or otherwise intrigue her. She 'collects' them by keeping them as her friends or at least stay on good terms with her, in case they ever prove useful to her. 

First year

Grades
Charms: O

Potions
Avalon has not mastered any potions as of yet.