It is hard to earn Therru's trust easily, probably due to being abused by her birth parents. She is tough when she needs to be, independent, and speaks her mind. While it takes a while to get to her center, she has a good heart and is very caring towards her acquaintances and any animal alike.
Therru has two strands of long brown hair in the front tied with red ribbon while the rest of her hair remains short in the back. She has scar on the left side of her face from where her previous parents burned her. Therru's attire consists of a plain dark pink jumper with a lighter, long-sleeved pink shirt under it as well as a white apron in the front.
She first appears when a group of slave hunters attempt to capture her, but is saved by Prince Arren. She then encounters Arren again, when he turns up at Tenar's house, accompanied by Sparrowhawk . Due to the friendship between Tenar and Sparrowhawk, Prince Arren is allowed to stay in Tenar's room for the night, as he is fairly weak. The next morning, Therru goes to wake Tenar, but sees Arren, filled with embarrassment and anger, she storms off and avoids him. When Cobb tries to strangle her to death, he believes to have succeeded and starts walking away until she tells him to stop. Cobb turns around, shocked to see that she is immortal. Cobb starts hobbling towards her rasping "eternal life" and tries to reach to her as if to take some of her immortality for himself. Before he can reach her, she transforms into a dragon and blows a ball of flame onto him. He catches on fire and stumbles back, triggering the already loose cut stone and falls to his death.
- Arren - Therru does not like Arren at first because he says he said "Life is nothing to me." when about to fight the slave traders. Therru later tells him she despises people who do not value life. After Therru is captured by the slave traders, Arren comes and rescues her. Surprisingly she does not show her appreciation to being rescued as she slaps Arren's hand away when he tries to help her up. She eventually accepts him and they team up to save Sparrowhawk and Tenar from Cobb. At the end of the movie she asks Arren to come and be with her again someday. Arren and Therru very close to each other. It is thought that Therru has romantic feelings towards Arren.
- Tenar - Tenar is like her mother and cares for her as if she is her own. She rescued Therru from the streets after her birth parents had abused her such as burn the left side of her face thus leaving a large burn mark (scar) on her face.
- Sparrowhawk - As Tenar reveals, Therru never talks to strangers, but after Sparrowhawks' arrival to their farm, he speaks kindly to her and after a little while she accepts him and also befriends him.