Gwen was born around 29 bX. It is unknown who her parents were, but her father is said to resemble Xorn. Most of her early life is unknown, but possibly around 5 to 12 bX, she arrives at the Forest of Thieves and joins the Thieves.
Gwen is with the group of seven Thieves that surround Xorn. Xorn kills six of them, but not Gwen. The two then journey together out of the Forest of Thieves. Later, Gwen fights in the war against Argon, and is saved from death at one point by Irunor. She and Xorn ride off into the east at the end of the movie.
Gwen, Xorn, and eventually their son live on the top of a mountain somewhere in the east, probably in the Wine Mountains. Gwen dies around 15 aX.
After trying to kill Xorn, Gwen joins him in his quest and quickly falls in love with him.
At one point, it is possible that Irunor is interested in Gwen, but a character tells Irunor "Be careful."