Ansem

Ansem the Wise was a famous scientist and sageking of Radiant Garden. To protect his people from the darkness he and his apprentices performed research and experiments to study the heart which resulted in the creation of the Heartless. Eventually Ansems apprentices were taken over by the darkness and when he decided to end the research they banished him to the Realm of Darkness and Xehanort continued the research in his name.