The lyrics of both the song and the epigraph that opens The Lord of the Rings books read:
“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.“
This poem is of course meant to outline one of the key pieces of Middle-earth history from the Second Age, shorthand that summarizes the drama surrounding the One Ring before the Fellowship’s quest to destroy it. While Tolkien was a bit vague on the details concerning the ringbearers representing the Men and Dwarves, he spent much more time exploring the three rings that went to the Elves. It makes sense, then, that the first magical rings created by Celebrimbor in The Rings of Power finale are the three that will eventually be worn by Galadriel, High King Gil-galad, and Cirdan (who is set to make his debut in season 2). By the time of The Lord of the Rings books and movies, Galadriel is the only one of these original ringbearers still wearing one, which is something that could eventually be explored on the show.
It’s no accident that the season ends with Halbrand/Sauron making his way to the land of Mordor since it’s in the fires of Mount Doom where he’ll forge the One Ring with which to influence all the other ringbearers. Until then, the song is a bit of excellent foreshadowing for what’s to come. It’s a great postscript for this love letter to Tolkien.