A world where, instead of aging in years, the people age in knowledge. So, instead of dying once a general age was reached, they die once they achieve a certain amount of knowledge. A man could live forever if he never learned anything, or could die after reading a few choice books. Of course, the knowledge of the land would be regulated, like medical drugs.
What if when a character died and the price to bring him back into the world was to allow an evil or good version to be placed in the world with the sole purpose of killing the character that just got its life back? The copycat character would die apon completeing his mission.....or would he?