Early in the 21st Cnetury,THE TYRELL CORPORATION advanced Robot evolution into the NEXUS phase---a being virtually identical to a human---known as Replicant The NEXUS6 Replicants were superior in strength and agility;and at least equal in intelligence,to the genetic engineers who created them Replicants were used Off-world as slave labor,in the hazardous exploration and colonization of other planets After a bloody mutiny by a NEXUS6 combat team in an Off-world colony,Replicants were declared illegal on carth---under penalty of death. Special police aquads-BLADERUNNER UNITS-had orders to shoot to kill,upon dedetection,any trespassing Replicant. This was not called execution. It was called retirement