A Guardian is a being that straddles the line between the living and the dead. They are often referred to as the living-dead. Becoming a Guardian is a conscious choice, unlike the transition to becoming demon-dead. A Guardian requires the consumption of blood to keep their body fresh and strong, but are also capable of many of the pleasures of the living, unlike demons.
Guardian's are capable of living for millennia, although it has been noted that they do age minutely.