Because The Lord of the Rings: The Rings of Power is set during the Second Age of Middle-earth, it can draw on fans’ knowledge of what will happen in the Third Age—and this is particularly apparent in Episode 4.

The latest instalment develops several of the show’s storylines, but the plot that stands out is about Prince Durin IV (played by Owain Arthur) and the discovery he has made in the mines of Khazad-dûm.

Why Durin’s Discovery in ‘The Rings of Power’ Means More Than You Think

In Episode 4, Elrond (Robert Aramayo) travels to the dwarven kingdom to talk to his friend Durin. The prince’s wife, Disa (Sophia Nomvete), claims he is elsewhere but the elf learns that Durin is really excavating an old mine.

When Elrond goes to confront him, the dwarf makes his friend swear that he won’t reveal to his kin, or anyone else, what they are mining for: mithril.

Fans of The Lord of the Rings, both J. R. R. Tolkien’s books and Peter Jackson’s films, will recall that mithril is an immensely strong metal. When Frodo Baggins wore mithril chainmail and was stabbed, the blade did not pass through the armor.

Durin tells Elrond that mithril is extremely difficult for the dwarves to mine and his father King Durin III (Peter Mullan) has warned him it is too dangerous to do on a large scale.

The king is right, because in Tolkien’s books mithril creates a big problem for his descendants, outweighing the benefits of the impregnable armor.

As Tolkien explains in The Fellowship of the Ring, Durin’s discovery of mithril created huge wealth for the dwarves of Khazad-dûm. Their greed led them to dig too deep, however, and they awakened a deadly creature: a Balrog of Morgoth.

Known in the books as Durin’s Bane, the Balrog was one of the Maiar spirits created by Morgoth, the first Dark Lord of Middle-earth. It fought alongside its master but fled into the mountains after the War of Wrath.

The Balrog slept deep within Khazad-dûm but awoke in King Durin VI’s reign, as the mining of mithril continued during the Third Age of Middle-earth.

The creature later killed Durin VI and his son Náin I, and their deaths led to the dwarves abandoning Khazad-dûm and founding the Kingdom under the Mountain, the realm that Thorin Oakenshield asks Bilbo Baggins to help him take back from the dragon Smaug in The Hobbit.

In The Fellowship of the Ring Gandalf faces the Balrog that King Durin VI woke up and it is during their fateful encounter that the wizard tells the creature it “cannot pass.”

Prince Durin in The Rings of Power is the grandfather of Durin VI, so it seems the Prime Video show is laying the groundwork for that king’s demise by showing the discovery of mithril.

Durin’s find will change Middle-earth for ever and is certainly more important than it seems at first glance.

The Lord of the Rings: The Rings of Power airs Fridays on Amazon Prime Video.