Filia was a priestess of the first holy order under Flarelord. She obeyed the orders of the elders at her temple, and as a result, she had a rather naïve and biased view of the world. Until she began traveling with Lina Inverse's party, Filia did not know of the barbaric acts of violence her race took part in around the time of the Kouma War.
Being a dragon, Filia has two bodies: her original golden dragon form, and the form we see most often, the young human woman. She can transform between these at will, but she does not enjoy transforming to dragon in front of other people, as it requires her to shed all her clothing in the process. Even in human form, Filia retains her dragon magic and skills, such as holy spells and the ability to teleport herself and others over fairly long distances. She also carries a large mace on a garter belt attached to her leg.
Near the end of Slayers Try, she gave up her priestess position, and by the time the whole Dark Star Dugradigdu ordeal was over, she found that she was the last remaining follower of Flarelord, the rest of her clan having been destroyed.
In the end of TRY, Valgarv was reborn as a pure ancient dragon, and she became his caretaker.
Out of all the characters, Filia is closest to Lina. They are good friends, even though they occasionally irritate each other. Filia became acquainted with Lina's sister, Luna Inverse, when she asked the Knight of Ceifeed to help her stop the impending doom. Instead of helping, Luna sent Filia to Lina, and the rest is history. Filia does not like how Lina and the others tend to forget about their responsibilities when a good meal or the opportunity to make money comes along.