The Soulless were a group that arose during the Miracle Day event, which had rendered virtually all humans on Earth incapable of dying. Members of the Soulless believed that because they could not die, they had been robbed of their souls.
Gwen Cooper first encountered the Soulless during a large candlelight vigil in Washington DC. Participants in the vigil walked silently and wore simple white masks depicting sad faces. (TV: Dead of Night)