sometimes there are babies that are born with two different eye colors. a long time ago babies that have such eyes were killed on the spot do to them 'being possessed by demons'. if a child was spared well you will find that a certain talent is enhanced. the child is then called a graceling and the enhanced talent is called a grace.
when a king found out such graces can be mind reading the killing of gracelings stopped.
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now in the present, people found gracelings a threat so they started killing gracelings. there is only one kingdom that still treats gracelings like a real person. that kingdom is Monsea. so now there is a war between gracelings and non- gracelings