Replicants are bioengineered humans, designed by Tyrell Corporation for use off-world. Their enhanced strength made them ideal slave labor. After a series of violent rebellions, their manufacture became prohibited and Tyrell Corp went bankrupt. The collapse of ecosystems in the mid 2020s led to the rise of industrialist Niander Wallace, whose mastery of synthetic farming averted famine. Wallace acquired the remains of Tyrell Corp and created a new line of replicants who obey. Many older model replicants--NEXUS 8s with open-ended lifespans--survived. They are hunted down and "Retired" Those that hunt them still go by the name...Blade Runner.