The round western room houses a magnetized platform and a Goron with armor and an attitude. Get close to the guardian, take a few swipes, and attack his belly when he raises his arms. After a few hits, he will roll into a ball. Put on your iron boots, face him, and wait for the beast to approach. Press A button to grab him when he gets close, and toss him left or right over the edge. When you've thrown him into the lava three times, you win.