Espers are magical beings that act as the way for playable characters to learn magic and summon powerful attacks in battle.
Espers were created as a result of humans coming into contact with Magic during their war for dominance. The gods decided to seal themselves away in the forms of statues and gave the espers back their free will, asking them to protect them while they slumbered.
A second war soon began between espers and humans seeking to use their powers, called the War of the Magi. When the war got out of hand, the espers created a new realm and escaped there with the Warring Triad's statues.
A thousand years later, a mysterious woman named Madeline stumbled upon the Esper World and fell in love with Maduin. Their forbidden relationship lead to the birth of a baby girl, named Terra.
Two years later, an army led by Gestahl, arrived in the Esper World. Unlike Madeline, who arrived by accident, Gestahl had spent many years in search of the place and immediately went to work capturing espers. The Elder, wishing to protect his people, formed a Sealed Gate around the entrance, forcing out all the soldiers. Unfortunately, Madeline and Terra were also pulled out, with Maduin following them. Terra and Maduin were captured, while Madeline was mortally wounded.