Yarvell was a Kaled female who lived towards the end of the Thousand Year War between the Kaleds and the Thals on Skaro. She was the daughter of Colonel Nasgard and Lady Calcula, the elder half-sister of Davros and the niece of Tashek.
She loved her father but resented her mother for constantly favouring Davros over her, and was disgusted by her brother's interest in animal life. At the age of 18, she was a member of the Military Youth. but was frustrated at how long it was taking for her to become an officer. She befriended Major Brogan when he brought Nasgard home to their house on Drammankin Lake. When he comforted her as she grieved her father's death, he revealed his pacifist ("peace activist") beliefs to her. She was devastated when she was forced to help execute Brogan, believing him to be innocent, and was horrified at Davros' request to have Brogan's body for experimentation. (AUDIO: Innocence)
By the time that she was 31, Yarvell had become both an officer in the Kaled Military Corps and a member of the peace movement. When she learned of Davros' part in a mission to destroy a Thal weapon development facility, she told some of her contacts in the peace movement, who warned the Thals of the attack. She did not want her brother dead, only removed from the war effort as she saw him as a threat to peace. She regarded him as "a dangerous psychopath." After Calcula tricked her into revealing the truth, she drowned Yarvell in the swimming pool at their home. Davros acquired her body for his experiments. (AUDIO: Purity)
Years later, after Davros was rescued from the Thal Dome by Nyder, he experienced an hallucination in which he conversed with his mother and sister, who spoke to him as if he were still a boy. (AUDIO: Guilt)