Sending

The Dead
When someone dies without accepting death before they do, they walk around as the unsent. They envy the living and that envy soon turns to hate and resent. They then react wiht the pyriflies to become fiends. To prevent them becoming fiends, the summoners must preform the sending which helps guide their spirits to the farplane. In some cases some dead can return from the farplane after being sent. This only happens when they still have a duty to fullfill.

Spoiler Alert!
The only 2 people that you've seen return from the farplane was Auron and Jyscal Guado. Auron needed to fulfill his promise to both Jecht and Braska. Jyscal needed to insure that his son, Seymore Guado, was stoped of his evil doings.