There are many incredible weapons in Middle Earth, from the elven bow gifted to Legolas by Lady Galadriel in Lothlorien, to the glowing swords Sting of Bilbo Baggins, and Narsil of Aragorn, to the Ring of power itself. The weapon lore of Tolkien’s world is almost as vast as his work on races, languages, and maps. But there are some weapons that play crucial roles in his books, that are never fully explained in the films.
Merry Brandybuck’s sword is a fundamental example of this. There are several small, but very significant details about the weapon laced throughout Tolkien’s writings in the trilogy, that never make their way onto the big screen, but these seemingly insignificant details add up to momentous importance in the desperate hour when Merry stabs the blade into the leg of the Witch King.
In order to understand why this particular sword is so important for this particular task, readers must trace the blade right back to its origins, and discover the journey of how it makes its way into the hands of the hobbit. For it’s not just any sword, but steel made in Westernesse, by the Numenorians who came across the sea in the earliest ages of Middle Earth. These noble men, who are Aragorn's ancestors, are known to have made some of the finest weapons of history, rivaled only by those that came from the ancient elven smiths of Gondolin. This sword has a lineage that even Merry is unaware of.
But of course, this sword is not a singular piece, it is one of four, and the other 3 reside in the hands of Pippin, Samwise, and Frodo. For these are the swords that the brave hobbits try to defend themselves with on Weathertop, where they are attacked by the 9 Ringwraiths. Frodo sustains a wound there that haunts him for the rest of his days, but without these swords, the situation would have been much worse, and could even have resulted in fatality. It is lucky then, that these swords were presented to the hobbits much earlier on in their journey, by Tom Bombadil, the mysterious forest dweller who lives in the ancient wood known as the Old Forest,von the edges of Hobbiton.
When the hobbits find themselves in danger and almost killed by the evil creatures of the Barrow-downs, Bombadil comes to their rescue. Once he has defeated the wights, he gives the four hobbits a sword each from the Barrow, before closing it for good so that no other unsuspecting victims may fall prey to the kings of old, the royalty of Westerness who were buried there and are now infused once more with an unnatural life in their dead bones.
So, Unknowingly, Merry has had this precious sword with him for the entire journey, but hasn’t as of yet, been required to use it. That is until he finds himself on the wrong side of the Witch King, and his fell beast, who are about to kill Eowyn. The brave shield maiden placed herself in between the Nazgul and King Theoden, who lies broken and dying on the battlefield. Eowyn fights to protect her uncle, but is almost crushed by the Witch King's black mace. In a last panicked effort to save his friend, Merry, who is on the ground and unnoticed, ‘stabbed him from behind, shearing through the black mantle, and passing up beneath the hauberk had pierced the sinew behind his mighty knee.’ At this, the enemy is paralyzed, rendered immobile for long enough that Eowyn is able to defeat him once and for all.
In the carnage that follows, Merry looks to pick up his sword, but when he finds it, ‘the blade was smoking like a dry branch that has been thrust into the fire, and as he watched it, it withered and writhed and was consumed.’ This description is remarkably similar to the Morgul blade that turns to dust in Aragorn's hands, and is symbolic of the blade disappearing because the magic that was in it has been spent in this last valiant attack.
What is truly remarkable about the blade, is that it was the missing key to destroying one of the most deadly enemies in Sauron’s service, for "no other blade, not though mightier hands had wielded it, would have dealt that foe a wound so bitter, cleaving the undead flesh, breaking the spell that knit his unseen sinews to his will." Thus Merry, whose worth in battle was doubted by so many, and who is all bust a simple hobbit from a simple life in The Shire, helps to win the War of the Ring, defeat Sauron, and usher in a new age of peace for Middle Earth.