With all four Elements in your possession, it's time to return to the Elemental Sanctuary, located within Hyrule Castle. This sacred place is where the Picori Blade can be reforged into the Four Sword, the only weapon capable of defeating Vaati.
After reforging the blade, you'll discover Vaati's true intentions and his transformation of Hyrule Castle into Dark Hyrule Castle. This final dungeon is a gauntlet of powerful enemies, challenging puzzles, and the ultimate confrontation with Vaati. stock up on health potions and Kinstone Fusions before entering, as this will be your toughest challenge yet. The castle is a dark and twisted version of its former self, reflecting Vaati's corrupting influence. Prepare for a series of intense boss battles and the climax of your adventure.