“She joined because her sister died fighting for Sigurd's army. The two were real close.”
—Amid telling Linda why Ethnia left Freege and joined Sigurd's army
Ethnia is the youngest daughter of Reptor and she is the mother of Amid and Linda. Her personality is more quiet, unlike her bright and cheerful elder sister Tailto. After hearing that her dear sister was fighting on the rebel army's side, Ethnia left in search of her.
If Tailto dies childless, Ethnia takes her in-story place in the second generation. This means, she is separated from Amid and she and Linda are forced to live with the Freeges, with Ethnia dying of both illness and depression due to her sister-in-law Hilda's abuse.
According to the Fire Emblem: Thracia 776 Illustrated Works, Ethnia was also the name of the Queen of Alster, Miranda's mother, who protected Leif and his friends when they visited Alster between the Year 762 - 765. However it is unclear whether she is the same person as Tailto's sister. The 20th Anniversary Fire Emblem Complete suggests that they are two separate people.
In Irish mythology, Ethnea is one of many variations of Ethniu.
- When crossing the Great River of Thracia, Leif mentions Ethnia as being the Earth Goddess. Whether Ethnia was intended to be named after this goddess or if this is just an oversight is unknown.