Death is not like the other abstract forces of Arken. Whereas the other powers are simply concepts and things come to life, Death is a power realized through souls of dead people (mostly, but not always, humans). A being serving the purpose of death must have gone through it him/herself. In this way death is not a "true" abstract, and unlike others does not stay the same entity throughout time, and can be destroyed. Time and Love wear the same faces and natures from the beginning to the end, but the power of each Death is passed on to another soul periodically.
Due to Arken being populated mostly by humans, nearly all Deaths are, have been and will be human souls. Some exceptions have sneaked in, most notably the six-armed Death of Violence - recorded as a feared figure in Western myths nearly a millennium ago.