Galatea Merrythought

Origin: Harry Potter
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Species: Human
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Residence: Krappweiss Street 55 (30-118)
Occupation: Teacher (Magical Defense), Author
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Import Date: 5
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Professor Galatea Merrythought was a witch and Professor at Hogwarts School of Witchcraft and Wizardry from around 1895 until her retirement in 1945. From some point between the 1920s and the 1940s, she taught Defence Against the Dark Arts.
Before her retirement, she worked alongside Albus Dumbledore and Horace Slughorn, her former students; after her retirement, Tom Riddle, another one of her pupils, was refused the chance to take her place, and so he vengefully jinxed the post so no professor could hold the occupation for longer than a year.

Biography
Early life
Nothing is known of Galatea Merrythought's past, although it is likely that she attended Hogwarts School of Witchcraft and Wizardry and would have purchased her wand from Ollivanders Wand Shop at Diagon Alley at the age of eleven.
She would have graduated at the age of seventeen and it is likely that she had high Defence Against the Dark Arts marks — almost definitely a N.E.W.T. in the field.

Career at Hogwarts
Early years
Merrythought returned to Hogwarts School of Witchcraft and Wizardry to teach sometime around 1895,[3] though what subject is unclear. Among her pupils was a young Gryffindor named Albus Dumbledore; other students she taught included Elphias Doge, Aberforth Dumbledore, Horace Slughorn, Theseus Scamander, Newton Scamander, Leta Lestrange, Tom Riddle, and Rubeus Hagrid.
The Headmaster during her early years was presumably Professor Phineas Nigellus Black, although she also went on to work under Professor Armando Dippet.
Having authored at least two books on the subject (Defence Against the Dark Arts, and Advanced Defence Against the Dark Arts, required reading when Albus Dumbledore was teaching the subject in the 1910s),[4] at an unknown point in her teaching career, certainly between 1927 and 1945, Professor Merrythought became the Professor of Defence Against the Dark Arts, taking ownership of Classroom 3C and an office on the sixth floor.
Many years later, when Professor Dippet was Headmaster, Galatea became the teacher of a brilliant student named Tom Riddle. Her fellow colleagues, and possibly Galatea herself, had been impressed by Riddle's skills and determination, and taught him all they knew.
During her fifth year of teaching Riddle, the Chamber of Secrets was opened and many of her students were petrified. Eventually, a third-year named Rubeus Hagrid was accused of releasing Slytherin's monster from the Chamber and he was expelled.
It was during this year that Galatea decided to retire, whether it was because of these events or not, and she left the school the following year.

Magical abilities and skills
Defence Against the Dark Arts: Professor Merrythought was an expert in fighting the Dark Arts, a highly respected DADA Professor at Hogwarts School of Witchcraft and Wizardry. She authored numerous books in the field, such as Defence Against the Dark Arts and Advanced Defence Against the Dark Arts. She was highly knowledgeable and accomplished in this branch of magic.