For years, the Shepherds ruled over the Lambs on the same planet, known as Terra. Then technology began advancing and the Shepherds left the planet and moved to a large aerial city in the sky called Cielville. That why they could still keep an eye on the Lambs but without having to have any direct involvement with them.
On Terra, life continued for the Lambs, without technology. They led simple, happy lives, building small towns and communities. Not all Lambs however were able to lead normal happy lives.
To run Cielville on a daily bases a large number of people were needed. The Shepherds were above manual labor, so therefore Lambs were taken of Terra, taken away from their friends and families to work as slaves in Cielville. The extremely rich, also had a large number of slaves at their deposal. Therefore it wasn’t uncommon for a shuttle to be seen, flying from Cielville to Terra, land in a random village and at random begin selecting Lambs to be new slaves to be taken to Cielville.