The Legend of Zelda: Breath of the Wild is packed with tons of “new” mechanics, which separate it from all previous iterations. One such feature, the weapon durability, is indeed one of the most polarizing features of the game, and has been seen as a sour note for more than a few reviewers. Every single weapon in Breath of the Wild can break and this includes the Master Sword, but the way it does is “unique” for the game at least. The Master Sword runs out of energy after you’ve used it enough times against creatures that aren’t the bosses; this causes the blade to go into a hibernation mode for ten minutes. Once the ten minutes are up, Link is allowed to use the sword freely until it once again runs out of energy. This does not, however, make much sense as we’ll find out throughout this story. [Editor note- this article contains spoilers, please proceed at your own risk]
The first key point we must observe is the history of the Master Sword. While no other game features weapon durability in the same manner as Breath of the Wild, it is important to note that The Legend of Zelda: Ocarina of Time has breakable weapons. The Biggoron’s Knife and the Deku Sticks would both break after an individual amount of use which limits their usability. Ocarina of Time, however, never has the Master Sword break or run out of energy. For that matter, neither does any game which features the Darkness Sealing Sword. There is never a precedent for such requirements, and frankly even Breath of the Wild seems to have tacked on the limit on the legendary blade. At times it feels like the restriction is in place simply to prevent players from only using that particular weapon. Yet, what if there actually is an explanation…?
In The Legend of Zelda: Breath of the Wild we’re treated to several cut-scenes in which Link is inferred to have used the Master Sword to kill an untold number of enemies. The best example of this is memory number five in which we’re treated to an image of various Lynels and Bokoblins dead from an attack on Link and Zelda. There are at least three White/Silver Lynels in the memory which each take a few minutes to kill since they’re “boss” tiered enemies. While the enemies signature weapons are visible, they’re all intact, and it is important to note that Lynels don’t ever drop theirs until death. This implies that the only weapon Link used during this incredible battle was the Master Sword, and to no ill effect. The Master Sword must have been at full power as well, since it’s clear that this wasn’t a regular battle either.
The answer, though, lies in the final memory of the game as Link lays dying in the arms of Zelda… and we see the Master Sword rusted and broken. At this point in the story, Link had used the blade so much its power started waning, and it’s demonstrated by the visible damage to the Master Sword. Even though it was at this moment when Calamity Ganon was finally free to wreak havoc, and the time when the blade’s power would be most useful, it became nearly useless. While some might argue that this is in fact a representation to Link’s overall health, I believe it’s something entirely different. The Master Sword is not a regular weapon after all; inside of it is the spirit of the sword, Fi. She was the one who instructed Zelda to take Link to the Shrine of Resurrection, and also the one responsible for the current status of the blade. This is because Fi can learn and adapt! A fact presented to us at the end of The Legend of Zelda: Skyward Sword, where we witness Fi mention emotions.
Everyone who has finished the game will know that Zelda placed the Master Sword at its altar in order for it to recover. Let’s presume that Link was awoken from his slumber once the sword had been fully restored. This would mean that it took the Master Sword a hundred years to come back to its original status. During this time Fi must have discovered that even she has her limits, and in order to prevent a repeat of those circumstance she must adapt to her new world. One in which Ganon has unbridled power. For this, she placed a limiter on the amount of energy she will spend on regular combat, but once she is in the face of Ganon’s evil, the limits would be lifted. This is the reason why the Master Sword becomes “unlocked” when in the presence of anything directly tainted/controlled by Ganon. Not only is the limit in place to prevent overuse, but also to ensure that she is present when the time to get revenge on Ganon is at hand.
Essentially, Fi is purposely limiting the amount of energy Link will spend as a fail-safe to prevent him from overusing her as he did a hundred years ago. This will also explain why Link is now expected to have a certain amount of hearts before wielding her. Fi wants to ensure that Link is prepared for combat without the Master Sword. Especially since by the time most players get it they would have at least gone through some bosses or the combat shrines. By preventing Link from simply going to the lost woods and getting his weapon back, Fi is ensuring that he is more than prepared for the times in which she is restoring her energy. All of this practically guarantees that Fi will have enough energy left for dealing the final sealing blow to Calamity Ganon. Once again, Fi has shown us her desire to protect her wielder by preventing him from getting into an unwinnable situation based on some statistical analysis during her time of slumber. It seems to me that Fi simply viewed this path as the most logical alternative…
P.S. A few questions have risen regarding the timeline of Breath of the Wild and the Master Sword. But I would like to remind everyone that Aonuma himself has stated that he doesn’t care where exactly or if it even fits into the continuity of the series. You can read all about it in Waypoint’s interview with the man himself.