THE RINGS OF BINDING
In the mid Second Age , Sauron the Maia recounted his repentance of past deeds as the chief servant of Morgoth and again committed himself to the domination of Middle-earth and its peoples. In S.A. 1000, he chose Mordor as the land that could most properly serve as the center of his realm and began the construction of the Barad-dur . From the first, Sauron recognized Numenor and the kingdoms of the Elves as his chief rivals for domination of the continent. To combat the growing influence of Numenor and her colonies in Middle-earth , Sauron realized he would need many powerful servants. As Morgoth's Lieutenant in the First Age , Sauron knew well how the hearts of Man might be turned against one another. To this end, Sauron devised the Binding Rings , powerful artifacts that could bind the spirit of a Mannish servant to Middle-earth indefinitely.
The three Rings of Binding which have dominated much of the history of Rhûn were relatively early works in Sauron's career as a ring-smith. When Sauron forged them he had not yet discovered the secrets that led to the more potent Rings of Power he would make in later years. For this reason, the Binding Rings impart to their wielders a great deal less than the Rings of Power , and carry with them important restrictions that make them inferior. For one, Sauron knew that the original bearers of the rings must have substantial power themselves, as well as a strong will and devotion to the service of Mordor. Secondly, the Binding Rings could neither extend the life of the bearer, nor allow the spirit of the bearer to maintain any physical form after the expiration of his body. Instead, the Binding Rings would bind the bearer's undead spirit to the ring after his body had expired. The spirit might then possess the body of the next bearer, assuming that the new bearer was not so strong-willed that he might resist the possessing spirit. Choosing a successor-host then, was a delicate matter where strength of body and mind had to be weighed against the strength of the will to resist. This was a matter that was not completely understood by Sauron and his servants until many centuries later.
By the end of the thirteenth century of the Second Age, Sauron completed several Binding Rings and was ready to begin the long search for a suitable Mannish servant to become the first bearer. At the time, however, his attentions were being drawn to the more urgent and promising matter of binding the Elves of Eregion , and so Rhûn was spared for some years more before Sauron was able to properly focus on the task of subjugating its peoples.