Link finally arrives at the last dungeon in "The Legend of Zelda" just to watch Ganon disappear before his eyes. Even after surviving several other dungeons fraught with danger throughout Hyrule, it might seem hopeless to try and fight an invisible enemy. Don't panic, though; as long as you can anticipate Ganon's general attack pattern, you won't be as outmatched as you think.
Enter the final room of the dungeon. In this dungeon, the room is dark; Link briefly holds up the Triforce before Ganon disappears for the fight.
Move out of the way when you see the first energy ball firing. You'll take damage if you get hit, of course, but there's something else important about this; the source of the ball gives away where Ganon is currently standing.
Strike Ganon three times. Each time you successfully hit him, he'll briefly reappear before resuming his hidden attacks. After the third one, make sure your bow and a Silver Arrow are equipped to the "B" button.
Strike Ganon a fourth time; this time, he'll appear a different color, and you can fire an arrow to defeat him once and for all—well, until the next adventure in Hyrule, of course.
If you're stuck with a melee sword but have high health, you can also try running directly toward the energy bullets; when you take damage running into nothing, you're hitting Ganon, so swing that sword.
Despite what the skull design on the floor suggests, you can walk all over the floor including the black tiles.
The number of times you need to hit Ganon depends on which sword you have equipped. With the Magical Sword, it's four in total. With any other blade, it's far more, so make sure you're coming prepared.
If possible, entering this dungeon at full health works best in your favor; you can use the sword beam technique to attack at range without having to worry about running headfirst into Ganon's bulk. Otherwise, you're stuck having to get as close as possible.