Catherine Volvagia was a powerful witch that was exiled from her magic town, this because every witch was born with an unique ability, but hers was the one of being able to eat every living being and absorb the parts of her victims to herself. The true reason she was exiled was because after going through puberty she ended up having a thin and flat figure with A cup breasts compared to the rest of the witches.
One day she was being annoyed by Olivia, a busty witch that shared magic classes with her, eventually Catherine proceeded to eat her completely, everyone else couldn't believe it as no one knew her true ability, after quickly engulfing and digesting Olivia, Catherine's chest began to inflate to a D-cup pair as her body gained mass, turning into a replica of Olivia. The town decided to expell her due her dangerous and evil potential, Catherine developed a hate for people and isolated herself, learning more about her powers. Since that day she was known as "The Vore Witch."
Catherine decided to explore the world by her own for years while keeping Olivia's attractive body instead of her flat original one, not making contact with any civilization, dedicating to make herself stronger to use her terrifying ability. She discovered that she could absorb ANY living being, this included plants and animals, capable of for example, eating a snake and then shapeshift herself into one, and with the help of her magic and spells could turn temporarily giant, making easy for her to collect her preys, eating many kinds of predators to collect many forms as possible. She also discovered that she could mix parts of the things she already ate, like a lion with tentacles or a big anthropomorphic animal mixing her human parts with animals.
The Vore Witch became a legend in her town as many years passed, at this point Catherine was in her 30s but didn't eat a single human more than Olivia. Until one day she discovered a city of non magic people, and could see there was many attractive women. She decided now was time to begin her hunt as her appetite grew exponentially.