- "When I lived, I was Emerald Slytherin."
- — Emerald Slytherin relays some of her past
Emerald Slytherin was a pure-blood witch, the younger sister of Salazar Slytherin, co-founder of Hogwarts School of Witchcraft and Wizardry and a ghost of Slytherin House. She attended Hogwarts as one of the first students and was sorted into Slytherin, where she taught Potions. During her time at the magical school, she befriended Helena Ravenclaw. At some point after starting her education, Emerald stole her brother's staff in an attempt to make herself unique from her brother instead of just being known as "the sister of Slytherin" and ran away to Black Forest. Her brother eventually left Hogwarts but, after becoming fatally ill, he returned to the school and, hoping to see his sister one last time, sent Minverin Pertran, a man who harboured an unrequited love for Emerald, to find her. In a fit of rage, the Minverin murdered her when she refused to return with him, before he committed suicide out of regret for what he had done.

Salazar Slytherin, her older brother
Emerald and the Minverin eventually returned as ghosts to Hogwarts Castle, where she became and continues to be a Ghost of Slytherin House.
During her time as a ghost, Emerald met a young Ilvermorney student who had been part of a exchange program named Isaac Nasser (who was in fact a descendant of Emerald's brother). Charmed by his sympathy and feeling a kindred spirit with the boy who was, like her, a loner, Emerald eventually disclosed the location of the hidden Staff of Slytherin, yet remained a friend of Isaac during his exchange term. Isaac, however, would later rise to became the greatest dark wizard of all time and master of the Death Eaters after his feeling of resentment regarding how his younger siblings overshadowed him due to his loner attitude and claimed the Staff, a tale Emerald later told to Iiron and Yellow years later during the Second Battle of Hogwarts. She also noticed the likeness between Yellow and her grandfather Isaac.
History[]
Early Life[]
- "I stole the Staff. I sought to make myself cleverer, more important than my older brother. I wanted to be known as more than just the sibling of Slytherin. I ran away with it. My brother, they say, never admitted that the diadem was gone, but pretended that he had it still. He concealed his loss, my dreadful betrayal, even from the other founders of Hogwarts, even after he left the school. Then my brother returned to the school — he was fatally ill. In spite of my perfidy, he still loved me and was desperate to see me one more time. He sent a man who had long loved me, though I spurned his advances, to find me. He knew that he would not rest until he had done so."
- — Emerald recalls her theft of her brother's staff
Meeting her first distant relative[]
- Iiron Scamander: "You've already told someone this story, haven't you? Another student?"
- Emerald: "I had... no idea... He was... flattering. He ... understood by loneliness ... my desire to be remembered ... he sympathised ...."
- — How Isaac managed to wheedle the location of the Lost Staff

Emerald Slytherin tells Iiron Scamander her tale