Forging a Sword
Forging a Sword is one of the 'Level 4' "Golden" Chamber Dungeons. The chamber dungeon is unlocked after Link completes the Ticking Clock dungeon.
The dungeon starts with 2 pre-determined tiles, one at the bottom-left and another at the top-right. Link will need to fill in all 25 other tile locations to complete the dungeon, two of which require treasure chests. The dungeon itself is in the shape of a sword, which is where it gets the title from.
Link will earn a Gold Rupee, worth 300 Rupees, for arranging and then completing the dungeon.
The sword's not done until it's all filled in. Start at the bottom left. Then work your way up and to the right. Master arrangin' it and you can have something'.