Character

Eiko Carol is the last known survivor from the lost summoning village of Madain Sari. She had been living her entire life in the village with only moogles, and got food by stealing from the merchants in the neighbouring village of Conde Petie. This lasted until Zidane appeared and accepted Eiko to his party, thus being the first human contact she has had so far. Eiko has summoning horns poking from her head, which proves her heritage.

After her adventures with Zidane and the merry bunch, after saving the world of Gaia, Eiko decided to continue her adventures alone. She bid farewell to her friends and family (moogles), and left.
It has been 10 years since she left, little is known where she has been during that time, but she has appeared back to everyone's knowledge after finding a portal deep within Gaia, directly opposite side from the well of souls that worked as kind of a portal straight to Terra earlier on her adventures with Zidane.
Her story in Eorzea began on the exact same day she decided to risk it all, and stepped in the portal. She decided to change her name a little, a new name for the new world. Maybe some day she will find a way back to see her friends, who knows.

Eiko is now 16 years old, but despite being entirely isolated to Madain Sari and Conde Petie for her young age and adventuring alone for 10 years, she has a very worldly attitude. Many of her thoughts of how people are expected to act - most specifically, her thoughts involving love - are shaped by theatre plays by Lord Avon, the bard.

Eiko has carried a scroll with her for the entire time she has been away from home, it's the single most important item in her life, she will risk everything to keep it safe. It's the message her parents had left for her before they were killed along with the entire tribe, except Eiko (and Sarah, Alexandria's former princess and current queen, who weren't known to originate from a Summoner Tribe).

"Eiko, You are a treasure born to a dying village. We are dying, and there is little we can do for you. We shall return to the stars with one wish in mind. If legends are not born of eidolons, and eidolons but born out of legends, let us leave this place with one wish: If we can give birth to a legend, it shall create an eidolon that is friend and protector of humans."
—Eidolon Wall in Madain Sari