Shiro'ken are spirits of departed mortals that have been summoned back to the mortal world and bound in a physical shell to the service of their master. Shiro'ken is the Canthan name for bound spirits that serve Shiro Tagachi's will. In Factions, Shiro Tagachi abuses his power as an envoy (which gives him great powers over the souls of the dead), and binds spirits to his evil bidding.