ヘラの塔のデグテール

Having patience is probably the biggest factor in beating Moldorm. You must strike the mammoth creature's tail six times with your sword to defeat it. Watch out for the rebound backlash, though—you might fly back and fall over the platform's edge. After you beat Moldorm, you'll receive a Heart Container and the Pendant of Wisdom.

You're more likely to fall from the battle platform than to lose all of your health. If you fall off, you'll plummet to the floor below and have to start the whole battle over again.