Ansem, Seeker of Darkness

Ansem, Seeker of Darkness, sometimes referred to as Xehanort's Heartless, is the main antagonist of Kingdom Hearts and the "Reverse/Rebirth" scenario in Kingdom Hearts Chain of Memories, as well as a supporting antagonist in Kingdom Hearts 3D: Dream Drop Distance and Kingdom Hearts III. He is a member of the real Organization XIII and the Heartless of Terra-Xehanort, and as such his appearance and personality are primarily derived from Master Xehanort, and he retains his original form's "shadow".

Ansem was created when Terra-Xehanort, masquerading as Ansem the Wise, reawakened his sleeping memories and split his heart from his body, creating a Heartless; this Heartless, also named Ansem, appears to have characteristics of both Emblem and Pureblood Heartless, and it is unclear exactly which category he falls under. However, because Terra-Xehanort did this of his own will, he retained his memories in his new existence, and gained the ability to control the other Heartless. With their power, Ansem attacked the Realm of Light, intending to have the Heartless consume the hearts of every world and lead him to Kingdom Hearts.