Stag Beetles are an enemy found in Phantom Hourglass, primarily in the Temple of Ice. They have strong masks that protect them from frontal attacks, similar to Helmasaurs from other games. In order to damage the enemy, Link can either attack it from behind or de-mask it with the Grappling Hook. With its mask gone, the Stag Beetle attempts to flee, posing little threat to Link. A single sword strike is usually enough to defeat it.
Stag Beetle from Phantom Hourglass