This article is from the Final-Fantasy and other Square Soft Games FAQ, by email@example.com (Nick Zitzmann) with numerous contributions by others.
The destruction of an intergalactic space ship lead to the population of
the previously uninhabited continent of Ignas. The north nation, Kislev,
has been at war with Aveh, the south nation. It was then that the Church
(aka "Ethos") discovered ancient fighting robots known as "gears," and
so, armies on both sides dug up & deployed these gears to aid their war
efforts. Later, the government of Aveh was taken over by a mysterious
high-tech force known as "Gebler," who continued to fight against
Xenogears tells a story about Fei Fong Wong, a small-town young adult
with a gift for visual and martial arts. Fei's two best friends, Timothy
and Alice, are marrying each other. On the day before their wedding,
though, their village is mysteriously attacked by gears. Unable to
resist, Fei climbs into an empty gear, unaware of the cruel destiny
which awaits him...
The most unique feature of the game is the actual battles with robots.
During the course of the game, each character acquires one gear which
they can call during combat to use against larger & stronger enemies.
Gears do not actually "level up" but acquire their power by purchasing
better parts for them to use.
This is also the first Square game to have hand-drawn anime movie
sequencies instead of having pre-rendered movies exclusively.