It is only two lines of a verse long known in Elven-lore:
Three rings for the Elven-kings under the sky,
Seven for the Dwarf-lords in their halls of stone,
Nine for Mortal Men doomed to die,
One for the Dark Lord on his dark throne.
In the Land of Mordor where the Shadows lie.
One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them
In the Land of Mordor where the Shadows lie.
He paused, and then said slowly in a deep voice: ‘This is the Master-ring, the One Ring to rule them all. This is the One Ring that he lost many years ago, to the great weakening of his power. He greatly desires it—but he must not get it.’
