Things You'll Need
Instructions
Talk to the man in the far northeast corner of Jim's Shack. It is assumed that you already have the Magic Shield from the Aqua Temple, or the man will have nothing to tell you. Talk to him about the Ruby.
Travel to the entrance of the Fire Temple, and go west from there. As you travel west, you should notice a rock that is slightly pink in color. You can approach it by following a narrow path between the cliff and the lava pools.
Use your Action button on the rock, and a message will pop up, asking if you want to take the Ruby. Say "Yes" and the Fire Ruby will be added to your inventory.
Return to Jim's shack and talk to the man in the far northeast corner again once you have the Fire Ruby. He will use it to make you the Fire Shield, which will save you from fireballs, fiery breath, and hours of yelling at a frustrating fictional Dragon.