Helmaroc King
In The Wind Waker
The Helmaroc King, also known as the Monstrous Helmaroc King, is an enormous bird seen wearing a hard metallic mask. He is a servant of Ganondorf in the Forsaken Fortress, and is also the primary minion sent out to search for Zelda. His appearance is similar to a Kargarok.
He appears early on in the game, being shot out of the sky by pirates while trying to capture the pirate Tetra. He drops Tetra and later captures Link's sister, Aryll, by mistake. It is later discovered that the Helmaroc King was bringing young and pointy-eared girls to Ganondorf in an effort to find Princess Zelda. Ganondorf wished to find the princess so that he could steal her piece of the Triforce. When Link travels to the Forsaken Fortress to save his sister, the Helmaroc King throws him into the sea at Ganondorf's command.
Much later in the game, Link returns to the Fortress to attempt to save Aryll once again. He successfully frees his sister and the other kidnapped girls with the help of Tetra and her pirate crew, though Link is attacked by the giant bird as he flees the flooding tower. The two fight when Link exits the top level, at which time Link may use the Skull Hammer to break apart the Helmaroc King's mask.
The Helmaroc King appeared once again in Four Swords Adventures. During this second appearance, he was yet again a boss that Link had to face at Mountain Pass.
The name of the Helmaroc King is most likely based off of the Helmasaur King, which also has a mask that must be destroyed before it can be defeated. The "Helma" portion of the word is probably derived from Helm or Helmet, while the Roc is a giant, elephant-eating bird of Persian mythology, and also the origin of "Kargaroc". Its Japanese name is "ジークロック, Jikurokku" which could be romanized as "Siege Roc", which is also the Japanese name for the Helmasaur King.
Strategy
At the beginning of this fight for vengeance, the Helmaroc King will flood the tower and follow Link as he runs along the wall to avoid the rising water. Right now, do the best you can to avoid the bird and the enemies along the steps of the wall. Just keep running until you get near the very top, where the bird will swoop down and stand right in your way. Take out the Skull Hammer and give it a good smack right in the face. It will scream and fall into the rising water, giving you the chance to climb out of the flooding tower. At this point, the floor of the tower will begin to close and the bird will fly up out of the tower to challenge you. This is where the battle really begins.
The Helmaroc King will perform three attacks. The first of these is where it lands on the ground, walks toward you, and attempts to smash you with its beak. If it misses you, the beak will get stuck in the floor. This will give you the chance to get out the Hammer and smash it on the helmet. This will produce a large crack on the helmet, evidence of the damage you are doing. (This is the move you want to wait for to deal damage.)
Its other two moves are: 1.) Flying around the tower and trying to run you over by scratching its claws on the floor. 2.) Floating in the air and flapping it's wings in an attempt to blow you into the spikes surrounding the arena.
After you hit it on the helmet with the hammer three times, it will crack and fall off. Now the bird knows its in trouble, and it will become much more frantic. Once again, wait until it tries to peck you with it's beak. While it's stuck in the floor, draw the Master Sword and slash it in the frill. After two or three times of this, the bird will display its death sequence by flying up into the air and exploding into black and purple smoke, rewarding you with a Heart Container.
Four Swords Adventures
In Four Swords Adventures, this boss was designed to stop you from entering the Tower of Flames. This monstrous bird would swoop down up Link twice, then drop rocks upon him and his clones, then repeat the process. To defeat this boss, Link would have to daze the bird with bombs to help him destroy the mask. After the mask was destroyed, then he could finish the job easily.
Super Smash Bros. Brawl
The Helmaroc King is featured as a trophy in Super Smash Bros. Brawl.