Cordelia is very tall and she is a spitting image of her father in looks. She has been having her hair in two braided pigtails since childhood. Cordelia is of very muscular build and very strong.
She is a well-mannered and shy person.
Cordelia was born as a son of Thorkell's to his unnamed wife in Ireland. However, when Thorkell wanted to take Cordelia to battle, the mother lied to Thorkell that "Halvar" (the name Thorkell had given his presumed son) was actually a girl so she would not have to fight on the battlefield alongside her father.
Her mother gave her the name Cordelia and then proceeded to raise her daughter as a woman. Cordelia grew up herself thinking she was naturally born female. However, as she grew older her appearance started to resemble her fathers. Although she wanted to keep on living as a woman, she could no longer pass for one and when Thorkell eventually came back to her hometown to marry her off to a husband he picked for her, she fled town with her mother.
Her mother sailed away with her, hoping that they would find a place where Cordelia could live freely. However, the ship sank and Cordelia was washed ashore, being the only survivor. Afterwards she became a slave of Halfdan's. She went by her male given name Halvar due to her appearance but felt uncomfortable having to hide her identity, so when Cordelia heard of Thorfinn's plan to sail to Vinland, she fled from Halfdan's farm in hopes to join him, so she could live the life she wanted. Upon telling her story, she also reveals her real name, given to her by her mother, "Cordelia". After this she is referred to as Cordelia by Thorfinn and his friends.
Cordelia's deadname "Halvar" might be an allusion to the Viking Captain Halvar, a character in the animated series Vicky the Viking, as the author Yukimura has made references to the Vicky the Viking series before, such as in Volume 1 of Vinland Saga.