An Exsphere is a key item from the Nintendo GameCube game, Tales of Symphonia. They are gems that are attached to the back of a persons hands, amplifying their power & fighting ability. However, attaching an Exsphere directly to a persons skin will cause them to grow sick and mutate. Because of this, anyone using an Exsphere in the game (Desians, Lloyd Irving, Kratos Auron) uses a Key Crest to mount the Exsphere in their hand, thus preventing gooey monster syndrome.
Later in the game Lloyd and friends learn that Exspheres are actually the products of human lives. The Desian farms, previously thought to just be labor camps, are where they gather up people to be harvested. The stress and hard living conditions in the camp bring out the power of the soul that eventually becomes an Exsphere in their processing plants.
When he finds this out, Lloyd becomes infuriated with the fact that his power in battle is the direct result of someone dying at the hands of the Desians. But he and his friends come to the conclusion that they must use this power to help defeat the evildoers, lest their lives be lost in vain.