Staldra

The Staldra is a three-headed Hydra-like Stalfos in The Legend of Zelda: Skyward Sword. They are extremely vicious creatures that were brought back to life as Stalfos solely by their thirst to cause pain. They are unable to die unless Link cut their three skeletal heads at the same time.

Battle
The Staldra mainly attack by lunging their three heads at Link to cause damage. Link must cut their three heads in one slice to defeat them for good. Should he fail, the other heads will simply regrow immediatly. The Staldra will often move its heads around to try to lure Link into missing at least one of its head. Bombs can also destroy their three heads if they are looking directly in the direction of the explosion. Link can also use his Shield to counter the Staldra's lunge and stun them long enough to prevent them from moving and allow him to cut all of their heads in one slice.

Fi's Comment
"This is a snake monster from before the dawn of time. Three bone-plated heads and a thirst to cause pain keep it writhing even beyond death. My analysis shows that to defeat this cursed snake, all three of its heads must be simultaneously destroyed."