Lethe is a loyal member of the Beast tribe in Gallia, and serves under Ranulf. She is a determined soldier, and always fights to see the victory for Gallia. She is Lyre's sister, and an old friend of Mordecai's. She tends to be more aggresive then the rest of the group, but that makes her the character that she is. She is later found out to train the new recruits of Gallia.
Lethe, as said above, takes her job to an extreme. She believes that her tribe is one to be proud of, and this makes her unable to tolerate criticism against her kind. Ike, on the other hand, shows her that beorc aren't all bad, and this opens her eyes to what the world could be like with Ike's invision. This creates a friendlier Lethe who tolerates beorc much more in the second game. She is still, and always will be, very proud of her heritage.