Due to him having intentionally separated his heart from his body and soul before he gave into the darkness, Ansem retained his self-hood, and intelligence after his transformation into a Heartless. Because he could think out his plans and pass for a human, he was able to destroy nearly every world in the Kingdom Hearts universe without revealing his identity, up until he confronted Sora at the Final Keyhole in Hollow Bastion. Due to his unique "birth", Xehanort's Heartless appeared to have characteristics of both the Emblem and Pureblood Heartless, though it is unclear exactly which category he falls under.