After their mother's death, Ethlyn took it upon herself to look after Sigurd and Byron since the two were quite slovenly men. She later married Quan and moved to Leonster to live with him. During their time there, she gave birth to their daughter and first child, Altena. Upon hearing about Verdane's invasion of Grannvale, she and Quan leave Leonster with Finn in tow and rush to Sigurd's aid, thereafter assisting his army in the rescue of her childhood friend, Edain.
In Chapter 2, Ethlyn mentions how fortunate Sigurd is to marry a kind person like Deirdre. Deirdre gifts Ethlyn with the Light Brand, which is eventually passed on to her son, Leif, and serves as his personal sword in Fire Emblem: Thracia 776.
Later, in Chapter 3, she grieves for Deirdre after the latter's sudden disappearance and asks Quan if the two of them will ever be separated. She also gives the Gáe Bolg to Quan, which she has carried since they left Leonster, but hesitated to hand over due to hearing about the Curse of the Gáe Bolg from his father. After taking refuge in Silesse with Sigurd for one year, she and Quan decide to leave along with Finn in order to bring back reinforcements.
Ethlyn and Quan appear again in Chapter 5, in which they arrive in the Yied Desert with the powerful knights of the Lance Ritter. She brings along a three-year-old Altena, despite Quan's discomfort, and convinces him to accept it. Once they discover that they are being followed by King Travant of Thracia and his Dragon Knights, Quan orders Ethlyn to escape with their daughter, but she refuses and instead gives him courage by saying that they can win if they fight together. Ethlyn perishes in the resulting battle, leaving Altena to fall into Travant's captivity, and Quan is slain as well.
|Fire Emblem: Genealogy of the Holy War Characters|
|First Generation||Sigurd • Alec • Naoise • Arden • Azelle • Lex • Quan • Ethlyn • Finn • Midir • Edain • Dew • Ayra • Jamke • Deirdre • Chulainn • Lachesis • Beowolf • Lewyn • Silvia • Erinys • Tailtiu • Claud • Brigid|
|Second Generation||Seliph • Lana/Muirne • Larcei/Creidne • Ulster/Dalvin • Oifey • Diarmuid/Tristan • Lester/Deimne • Julia • Fee/Hermina • Arthur/Amid • Iuchar • Iucharba • Shannan • Patty/Daisy • Leif • Nanna/Jeanne • Finn • Ares • Lene/Laylea • Tine/Linda • Febail/Asaello • Ced/Hawk • Hannibal • Coirpre/Charlot • Altena|