Carrow was born into the Carrow-family, a british wizaridng-clan who held up beliefs about pureblood-supremacy and dislike for non-magical people.
At some point in the 1920's she joined the cause of the dark wizard Gellert Grindelwald, likely due to her family-beliefs. In 1927 she traveled with Grindelwald, Vinda Rosier, Krall, Abernathy and several others to Paris, preparing for a rally that her master would hold at the Lestrange Mausoleum in the Cimetière du Père-Lachaise.
She notably helped her allies clear out a muggle-house, that would serve as temporary base. The wizards and witches killed the enitre family living in the house, with Carrow notably murdering an infant child.
She was later present during Grindelwald's rally and managed to escape in circle of blue fire when the battle between Grindelwald and the Scamanders began.
Other Wizards & Witches