Yrsa Kristjansdottir was a police inspector in Reykjavik during the 21st century. When she was a little girl, her father would read her stories from a book about trolls and hidden folk, however she never believed that the stories were true.
Two years after her father was killed by Sigdor for getting too close to discovering the truth about Hellion, She aided the Sixth Doctor in uncovering the conspiracy surrounding Hellion. (AUDIO: The Hunting Ground)