Originally, the Heartless exist within an all-encompassing variety, the "Pureblood". Before the events of the first "Kingdom Hearts", these Purebloods are typically only encountered in the realm of darkness, although people with a strong will may summon them to the realm of light. While studying the Pureblood Heartless, as a side effect of their research to control the mind through the heart, Xehanort and Ansem's other apprentices devise the means to create artificial "Emblem" Heartless via the corruption of living hearts, which are differentiated from Purebloods by an insignia on their bodies. Unlike Purebloods, Emblem Heartless release hearts once defeated. However, unless the Keyblade is used to defeat the Heartless, the stolen hearts go to the realm of darkness where they turn into Heartless again. This, combined with Maleficent's quest to gather the seven Princesses of Heart by using the forces of darkness, make the Heartless a common sight within the realm of light by the events of the first "Kingdom Hearts".