Later she becomes the Lady of the Lake, a powerful enchantress.
After being lost in Druma Wood by her mother, Elen, she was found by Cwen, a treeling. After a failed attempt to find Rhia, the kingdom gave up and presumed her dead. Cwen and Rhia lived in the ancient tree, Arbassa. She longs to regain the wings that Fincayrans lost long ago for an unknown reason.
While swinging around Druma Wood one day, she encounters Emrys, a strange boy she's never seen before. Skeptical of the stranger, she trapped him and was about to leave him. Emrys peaked her curiosity and they quickly became friends. They are joined by a feisty merlin (hawk) that Emrys had saved and healed earlier, who quickly was named, Trouble. After taking him back to Arbassa, he told her of his quest to find his real name, home, and history. They discover the blight, afflicting the rest of Fincayra, spreading to the Druma. She persuades Emrys to accompany her in trying to save the Druma. To learn what can be done to stop the blight, they travel to the Grand Elusa. En route they meet a very small giant named Shim, who joins their journey. After conferring with the Grand Elusa, they find that Cwen has betrayed them to the warrior goblins. Eventually Emrys is captured, but Rhia covertly takes his place, and Trouble goes missing. This prompts Emrys and Shim to rescue her. After much traveling and reuniting with Trouble, they find her in the dungeon of the Shrouded Castle. They defeat the wicked king Stangmar. His master, Rhita Gawr, is forced back to the Otherworld through the self sacrifice of Trouble, the merlin. Later, Rhia tells Emrys that he has found his true name, Merlin, which he decides to keep.
When she and Elen move to Avalon they found the Society of the Whole.When Elen dies she becomes the next High Priestess.