Essie was the eldest child and the only daughter of Ashildr and Tomas.
During the 14th century, Ashildr, using the alias Alys, met Tomas in France and married him. Essie was conceived accidentally, as Ashildr believed she did not want children. But on the day she was born, Ashildr fell in love with her, and decided to have two more children, Johann and Rue, so that they can comfort each other on the day Ashildr would have to leave them in order to protect her secret.
Ashildr, having become wary of Tomas's growing comments related to her immortality, took Essie and her brothers on a boat from France to Britain in 1348, much to Essie's confusion, being an inquisitive child. She was annoyed that her mother wanted her to learn and speak in English instead of French, though she was infatuated with the idea of drinking tea. During the voyage to Britain, Essie and her brothers caught the bubonic plague. Ashildr tried to decide which one of her children to save with the second Mire medical Patch, but ultimately decided to let all three of them die. (PROSE: The Triple Knife) She kept the pages in to remind herself to never have offspring again as they would all die eventually.