When i played the a link to the past in the four swords game i find out then when you go to the dark world. and to the piramid you can enter the temple of the four swords.
when you look then at your cristals you see four swords!!
Okay, all you have to do is beat ALttP and Four Swords and you can get into the dungeon. You have to defeat four bosses to recieve all four swords, and then you have to defeat four Doppelgangers of yourself. Really a challenge if you try beating the Palace of the Four Sword with the green mail and Master Sword. Guess who's done it!