Master Ore #1 - Sewers
The first Master Ore is found inside Lorule's Sewers. To get there, you'll have to merge through a rift near Hyrule's Sanctuary or Graveyard. Once in Lorule's Graveyard, look for a large boulder just north of the weathervane. Life this to reveal the Sewers entrance.
This mini dungeon is laid out identically to Hyrule's Sewers, so proceed through like normal. Eventually, you'll fight a trio of cyclops statues. Take them out to continue forward, then pull the eastern switch in the next room. Take the stairs that open up to a secluded part of the Lorule Sanctuary. Merge across the gap to the big chest up here to find a Master Ore inside.
Master Ore #2 - Dark Palace
To get the second Master Ore, head to the top floor of the Dark Palace. When you reach the top floor (see our dungeon guide for more information), head to the southern room where windows run the room's perimeter.
In the center of this room are two orbs. The top one lifts and lowers a platform nearby, and the lower one rotates a wall near the same platform. Place a bomb near the lower orb, then quickly hop aboard the platform; slash the upper orb to ride the platform up. Quickly merge into the wall here before the bomb detonates, and the explosion will activate the lower orb, rotating you into a secret room. The chest here contains a Master Ore.
Master Ore #3 - Skull Woods
The third Master Ore is found in Skull Woods. Head through the dungeon until you reach the room where you must carry the eyepiece back to the statue (for more information, see our dungeon guide).
From the outside area where you have to drop into said room, make a right at the fork and slash up these purple flowers. Drop into the hole here, Back inside the dungeon, merge into the wall and move west. Move past the eyepiece, and merge north to a narrow ledge holding a big chest. What's inside, you ask? Another Master Ore.
Master Ore #4 - Thieves' Hideout
The final Master Ore is found inside Thieves' Hideout. To get it, you'll first have to rescue Thief Girl and make your way to floor B3 (see our dungeon guide for more information).
Just before leaving the floor, use Thief Girl and yourself to activate these dual switches. This opens a up a long, secret passageway with a chest at the end. You'll find a final Master Ore inside.
Upgrading the Master Sword
With the Master Ores in hand, you can take that Master Sword up a notch. First, head to the Blackmsith in Hyrule. Give him two Master Ores, and he'll temper your blade into the Master Sword Lv. 2.
Now travel to Lorule and head to the Blacksmith there. When you approach, he'll remark about the quality of the blade and insist he can take it even further. Follow him inside the shop and give him the last two Master Ores. He'll turn your weapon into the ultra powerful Master Sword Lv. 3. Combine this with the MaiaMia baby upgrades, and you'll be an unstoppable warrior in no time!