The Shepherd Plan was a secret program undertaken by Paradeisos to harness the power of the Shackles; its name is derived from the other known wielder of the Shackles, the Underground Shepherd. The Shepherd Plan was begun shortly after the Eclipse Operation in late N.F. 103, in which Paradeisos recovered the required materials from the Lone Island in DisSea. The program likely sought to create modified clones of the Underground Shepherd, as it is stated by Schorl that Paradeisos once possessed cloning technology, but somehow lost it.
Almost nothing is known about the details of the Shepherd Plan, except that the Chief, under the codename Shepherd-13, is the program's final product. Despite this, the Chief is considered a flawed, defective specimen. The nature of these flaws is unknown, but Shalom believes that they possess qualities unlike any other Shepherd which allowed them to bypass the Hush system's technological barriers and break her emotional conditioning.
Little to nothing is known about the previous Shepherds before the Chief. One or more previous Shepherds were able to consume three Corpuses, but that number was the "historical limit". Shalom says that by consuming Corpuses, SHP-13 was "gradually approaching their origin."