I think that the effect of prolonging the lives of mortal bearers probably came from the Elves. Remember, it was the Elves themselves who forged the Rings, not Sauron. He taught them how to do it, and probably helped them, but he didn't do it himself. I think that whenever Elves make something, for example, a piece of jewelry, a little bit of themselves goes into their creation. I think that is what happened in the case of Celebrimbor and the other Elves of Eregion. Their desire to prolong and preserve what was beautiful inadvertently prolonged the life of the mortal bearers of the Rings of Power. The Elven Rings didn't seem to have any effect like that, because their bearers were already immortal.
__________________
But Melkor also was there, and he came to the house of Fëanor, and there he slew Finwë King of the Noldor before his doors, and spilled the first blood in the Blessed Realm; for Finwë alone had not fled from the horror of the Dark.
|