As a child, Eavan adored her father who often doted on her. Once, he gave her a book she especially liked; Eavan read it obsessively, leading her father to remark, "When you're done reading that book, tell me what it was about, okay?" to which she happily promised.
On the night of The Tragedy of Emain Macha, in the midst of the chaos, Eavan's father hid his daughter, asking her to remain silent where she was, and not put herself in danger. Despite Eavan's pleas, her father refused to remain with her, only telling her, "Remember to tell me what that book was about," before leaving her behind and moving to the flames that roared outside their house.
His body was eventually found, and Eavan's inductive reasoning led her to believe her dad tried to help others escape the destruction that was taking place over the whole city. She attended his burial with a solemn face and the precious book he had given her.
Although she held onto her belief strongly, while bullies had attacked her one day and tried to target her book, the bullies claim that there is no such thing as a person willing to help others at the cost of their own lives. Through their speech, they indirectly denounce her father as a coward and shattered her beliefs, and then proceeds to tear her father's gift apart.
This is the reason why she believes sacrifice is a meaningless concept, and one that no one should partake in. During the male Milletian's quests during Generation 3, she exercises this belief by discouraging the Milletian from taking risky actions, keeping an eye on them whenever he does, and on one occasion sending backup when it seems like the Milletian had overestimated himself. In the end, however, she accepts the Milletian as the adventurer he is, and she gives him a charm made out of her ring to protect him, so that if he is ever in danger it will not be he who will die, but she who is sacrificed.