Fi's spirit may continue to exist within the Master Sword in Breath of the Wild. Princess Zelda reveals to the Great Deku Tree that the Master Sword told her that her destiny was not finished, it convinced her to seal Calamity Ganon herself. In his vision after removing the sword, Link sees Zelda speaking to the Master Sword as if it was a person. She told the Master Sword that its master (Link) would come for it, like Fi whose spirit slumbers within the sword and refers to Link as "master" in Skyward Sword.
More than 100 Shrines of Trials to discover and explore - Shrines dot the landscape, waiting to be discovered in any order you want. Search for them in various ways, and solve a variety of puzzles inside. The tasks you must perform in each Shrine varies, and you'll never expect the challenges you'll face until you enter. Some will involve realistic physics, and some will require you to harness the power of nature, including electricity, wind, fire, and more. Work your way through the traps and devices inside, utilizing your runes and think outside the box to earn special items and other rewards that will help you on your adventure.
Breath of the Wild is notably the first and only game where Link and Zelda held feelings of animosity towards each other, until they learned to open up to one another. Once learning to do so, the two came to genuinely care for one another, with both Hylians refusing to sacrifice each other for their own safety, no matter what peril they may be in. This is to the extent where Zelda unconsciously awoke her powers (despite previously being unable to do so, no matter how hard she tried) by shielding Link from a Guardian`s attack, showing how much he means to her. When Link temporarily died, Zelda wept at his body, lamenting his death. Upon learning from the Master Sword that Link can be revived, Zelda wasted no time rescuing Link, while also deciding to use her newfound powers to hold Ganon at bay.
According to the in-game backstories, the world of Hyrule was created by the three golden goddesses: Din, Farore, and Nayru. Before departing, the goddesses left a sacred artifact called the Triforce, which could grant powers to the user. It physically manifests itself as three golden triangles in which each embodies one of the goddesses' virtues: Power, Courage, and Wisdom. However, because the Triforce has no will of its own and it could not judge between good and evil, it would grant any wish indiscriminately. Because of this, it was placed within an alternate world called the "Sacred Realm" or the "Golden Land" until one worthy of its power and has balanced virtues of Power, Wisdom, and Courage in their heart could obtain it, in its entirety. If a person is not of a balanced heart, the triforce part that the user mostly believes in will stay with that person and the remainder will seek out others. In order to master and control the triforce as a whole, the user must get the other parts found in other individuals and bring them together to reunite them. The Sacred Realm can itself be affected by the heart of those who enters it: those who are pure will make it a paradise, while those who are evil will transform it into a dark realm.