Terzie is the second daughter and middle child of Lord Barak and Lady Merel of Trellheim. Her estimated birth year is 5362-5364. She has an older sister, Gundred, who is described "only slightly older than Errand" (Castle of Wizardry) with long reddish-blond braids. Terzie also has these long reddish-blond braids. She is a year or so younger than Gundred.
By the time of the birth of Geran, she is described as hovering on the brink of womanhood: romping with the younger children one moment and looking the next with devastating eyes at the group of adolescent Rivan boys who always seemed to be around.