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Hermione has learned she's really a pure blood and lost child from House of Black

Her friends have turned on her and she's been placed in Slytherin house angry at those she thought where her friends

She decides that she will have revenge for their actions (I'll need a bit to work on this as I was asked the write this as a challenge but the person kept trying to direct where the story went I do not mind helpful advice but I firmly believe if you ask/challenge someone to write something then let them do it without trying to control it)