Helmethead

From Zelda Wiki.org

Helmethead
Game(s)	Zelda II: The Adventure of Link
Dungeon(s)	Midoro Palace
Weakness(es)	Jump Spell

Helmethead is the boss of Midoro Palace, where Link recovers one of the six Magic Crystal shards necessary to rouse Princess Zelda from her unnatural slumber. His weak spot is his head. It will fly off his neck and start attacking with projectiles.