Esper (Final Fantasy VI)

An esper (幻獣, Genjū lit. Phantom Beast) is a magical being from Final Fantasy VI. Espers act as the means through which Magic is learned in the game, and as the game's Summons.

History
Espers were created as a result of humans coming into contact with Magic and the Warring Triad during their war for dominance. The gods eventually realized what they were doing was wrong, and they decided to seal themselves away in the forms of statues. They gave the espers back their free will, and asked them to protect them. Later a second war began between Espers and humans seeking to use their powers, beginning the War of the Magi. At the height of the war the Espers created a new realm and escaped there with the Warring Triad's statues. A small handful of Espers remained in the world, such as Valigarmanda who was frozen in ice, and Odin who was petrified in the Ancient Castle buried deep within the mountains. Ramuh lived in the human world for an unspecified time, using his humanoid appearance to blend into normal society, and he implies other Espers do the same. Magicite remains of Espers also remained, such as Ragnarok and Phoenix. As a whole however, magic faded from conscious mind and became the stuff of legends and myths.

1000 Years Later
The espers had lived in their world, safe from human invasion. However, one day, a woman named Madeline stumbled upon the esper world and fell in love with an esper named Maduin, much to the other espers' dismay. She gave birth to a baby girl, and named her Terra.

Two years later, an army of humans, led by Gestahl, came into the esper world. Unlike Madeline, who had come upon the place by accident, Gestahl had spent many years searching for the Esper World. Almost immediately, his troops began capturing espers, causing a panic. As a result, the Elder, who was one of the few descendants able to perform the feat, formed a Sealed Gate around the entrance to the esper world and force out the soldiers. Maduin was taken as well when he tried to stop Madeline and Terra from leaving the esper world before the gate closed, as Gestahl captured all three of them, but killed Madeline.

For the next sixteen years, espers were being held in labs in the Imperial capital of Vector, and were the subject of horrible experiments conducted by Cid Del Norte Marquez, who experimented with extracting magic power from the espers and infusing them into humans using the process of Magitek. His first experiment was done on a man named Kefka Palazzo. The experiment was a failure, as Kefka would later become twisted as a result. A more refined process was later invented and used on Celes Chere, who Cid raised as his daughter. However, though the process was no longer mentally harmful, it would not completely transfer an esper's power. The espers have to be reduced to Magicite if their power is to be completely drained. This is discovered when Locke Cole, Celes, and two others try to rescue the imprisoned espers from the Magitek Research Facility. As a result, Emperor Gestahl begins to look for ways to reopen the Sealed Gate, and uses Terra and her friends to do it. Eventually, most of the espers are turned to Magicite and put into Kefka's hands, and he uses his new power to revive the Statues, slay the Emperor, and cause the apocalypse. After Kefka is defeated the remaining espers die out, as they cannot exist without the Statues, the source of Magic.

List of espers
Esper (FFVI)