The first Shifters created by Adonai and the other Divine, were called Purebloods. They had to be granted a spark of the Divine and given the Voice. This granted them access to magic like the Divine used. This was done when the Divine Jeduthun sacrificed himself and fragmented his Voice so that it could be bound each of the first Purebloods. As generations passed this spark was absorbed by the human form, bonding with the blood. When this happened the Shifter lost access to the Voice.
However, a few time in each generation a Shifter is born with the Voice. These are the Purebloods, the few who have the spark of the Divine in its purest form. They can use their Voice and can live longer than normal Shifters. One common aspect of Purebloods are their gold-flecked green eyes.