A group of Stilean flesh eaters crashed on Earth at some point before or around the 1500s. Their leader, the oldest among them, was concerned only how to keep her people alive and fed. She first encountered the Thirteenth Doctor and Team TARDIS in Guelder, where she took a bite out of the Doctor's arm. After consuming the Doctor's Time Lord blood, the flesh eater realised she had begun to age at a much slower pace, resulting in her continuing to live for centuries, watching her friends grow old and die as she did. Throughout her extended life, she raised "generations" of children, and continued to learn more about the humans her people had been preying on, to the point that she had taken a liking to them.
In the 2010s, the flesh eater, now known as Bethany Brunwine and residing in London, began her historical podcast series, Hidden Human History, which talked about the lesser-known conflicts of Earth's history, inspired by the Doctor's prior statement about history: "all of the actual people get lost in the numbers and the names". Brunwine explained it all to the Doctor, along with Ryan, Yaz, and Graham when they all paid her a visit at her home in 2019. (COMIC: Hidden Human History)