Eve was known as "The Little Queen of Nasods" back when humans and Nasods coexisted peacefully in Ancient Elrios. She spent thousands of years frozen in a capsule to protect her from the catastrophic war that eventually broke out between the two races. When an El fragment crashed into her unit, she finally woke up—only to find herself completely alone in a world she didn't recognize anymore.
With whatever strength and ancient knowledge she had left, Eve set out to revive King Nasod and restore her entire race. A queen needed her king, and she understood that deeply. For a while, it seemed like it might work.
But things fell apart quickly. King Nasod and his followers became consumed by the old grudge against humanity, grew corrupted, and stopped listening to Eve entirely. They continued the ancient war regardless of her wishes. Then a young red-haired boy and his companions showed up and systematically destroyed what remained of the Nasod race, including King Nasod himself. Eve was left stranded again, alone in a time period she didn't belong to, with all her efforts seemingly for nothing.
She didn't give up, though. Eve decided to pursue the El Shards herself and use them to regain enough power to bring her race back. More importantly, she made the choice to follow that red-haired boy and his friends. It was the first time anyone had actually offered to be her friend, and that mattered to her.
Content compiled by AnimeList.moe from publicly available sources.