When you fall in the hole that the bat made, Ganon will be there. Before he can talk to you, strike him with your Golden Sword. After your conversation, approach him and strike him six or seven times while dodging his trident. He will teleport. Instead of throwing his trident, he will release about eight small fireballs that turn into fire bats. Use the Cane Of Byrna or the Magic Cape to attack him instead of dodging around. You must do this over ten times. He will teleport again. If you fail to attack him first, he will release a fire bat that will make a spiral of flames. If you hit him first, he will make a quake on the ground. The upper left floor will collapse. Do this four times. The border floor will become a hole. He will tell you that you can fight the Secret Technique of Darkness. After that, the lights will go off. Use the Firerod or Lamp to light the lamp stands. Then, immediately strike him. Then, immediately change your item to Silver Arrows. You can hit him two times if you are quick enough. It takes four arrows to destroy Ganon. If you were slow in stunning him, just light the stands if the fire goes out. You can defeat Ganon even you do not have medicine.