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Rings seem to be rather important in The Lord Of The Rings, but what do magical rings do in general? I don't mean the side effects of wearing the One Ring (invisibility, long life span) but the intended effects of rings. Based on Saruman's creation of his own Ring, they can't all be for the purpose of enslaving the races of Middle-Earth. Reading this article on the Rings of Power suggest they help the wearer become awesome at tasks that the wearer would try and undertake normally (Dwarves gathering money, Gandalf's helping him lead).