Iron Knuckle

The Iron Knuckle is one of the largest, stockiest foes in The Legend of Zelda franchise, however, only appears in The Adventure of Link, Ocarina of Time, and Majora's Mask.

Characteristics
The Iron Knuckle is a large heavily armored knight, equipped with a sword or axe capable of dealing immense damage. Though quite similar to Darknuts, Iron Knuckles are less common across the series, and usually play the role of stoic guardians as opposed to the more aggressive behavior of a Darknut. The main difference however is that they do not share a Darknut's traditional weakness to attacks from behind. These foes are dueling elites, incorporating much of the same swordplay technique Link does during battle to great effect. These creatures are also known for their unmatched defensive capabilities and long vitality. In their debut, The Adventure of Link, these knights predominantly appear in the temple dungeons where it is said they were "iron warriors" chosen by the King of Hyrule. They fight with both sword and shield, and appear in three varieties of increasing strength: orange, red, and blue, with the Blue Iron Knuckles being capable of shooting Sword Beams. In later titles, Ocarina of Time and Majora's Mask.

The Iron Knuckle appeared later as minibosses in Ocarina of Time and Majora's Mask, in the former appearing as a facet of the plot at the Spirit Temple, and in the latter as guardians that appear predominatly under the Ikana Graveyard, protecting tombs. They were distinguished from Darknuts of previous games by their use of huge axes, capable of taking four hearts from Link at every swing, making them the strongest recurring enemy in the games. Their grand size and armor coverage also meant they took many hits to defeat, but their slow attacks and recovery are their weakness. Like in Zelda II, they also come in varying strengths and colors, with one in particular being larger and having more extravagent armor.

Rebonack
In The Adventure of Link, a Blue Iron Knuckle called  is the boss of the Island Palace. This boss is also known as "The Guardian Ironknuckle" or simply "Ironknuckle", but The Official Nintendo Player's Guide refers to him as Rebonack, an alternate translation of his Japanese name. He rides a floating steel horse and wields a lance, and charges at Link at a high speed. Seemingly on the back foot against a mounted opponent, Link must use the Down Thrust initially to damage him and his horse. After enough damage is done, he dismounts his horse, and can then be fought as a normal Blue Iron Knuckle. Two more Rebonacks appear as minibosses in the Three Eye Rock Palace, one of which guards the chamber containing the Cross and the second appearing before the pit that leads to the boss, Barba.

Plot Significance in Ocarina of Time and Majora's Mask
In Ocarina of Time, Nabooru is captured and brainwashed by Koume and Kotake, a pair of Gerudo witch sisters. Koume and Kotake then force the brainwashed Nabooru to don armor and protect the entrance to the final chamber in the Spirit Temple as an Iron Knuckle. This Iron Knuckle is larger than the previous ones, and wears slightly different armor. When Nabooru is defeated in her Iron Knuckle form, the armor falls away and reveals her, apparently releasing her of her hypnosis. The fact that the other two Iron Knuckles in the Spirit Temple dissolve completely when they are defeated suggests that they were animated by magic and not hypnotized people, like Nabooru.

In Majora's Mask, there are only three Iron Knuckles: two are beneath the Ikana Graveyard on the first and second day respectively: one is guarding the resting place of Flat and the other is guarding a Piece of Heart. The third is on the Moon in the hide and seek game played by Link while in his Hylian form. Also in Majora's Mask, gold Iron Knuckle armor can be seen on display in the Curiosity Shop. The significance of this armor is unknown, but it is interesting to note that the armor wields a sword like their appearances in The Adventure of Link, not an axe.

Weaknesses
Iron Knuckles in The Adventure of Link are experts at defensive strategy, using a shield they constantly move up or down to block Link's attacks while also attacking high and low. Link must also focus on defense and watch the swing of its sword and block accordingly while looking for an opening. He should use the Shield magic to protect himself when fighting them. It is also possible for Link to jump and perform a low stab at its head to inflict damage. In Ocarina of Time and Majora's Mask, they are particularly weak to Jump Attacks while they recover from failed axe strikes. The armor of the Iron Knuckle can be damaged, providing two stages to every battle. While wearing armor, they're slow and impervious all attacks save for sword swings and Bombs. Once enough armor is removed, they become enraged and move quicker, but are now weak to arrows, opening up the opportunity for a successful long-range strategy. Despite their similarity to Darknuts, it is not recommended to attack an Iron Knuckle from behind, as they can perform a fast, deadly spinning attack to counter such a strategy. Nayru's Love is particularly useful when fighting Iron Knuckles due to the extensive damage they cause.

Captain N: The Game Master
The Rebonakku appears in two episodes of Captain N: The Game Master. He is first shown in "Quest for the Potion of Power" after Link, Princess Zelda, and Kevin arrive to the chamber of the Potion of Power in Island Palace, where the Rebonakku reveals himself to be the guardian of the potion. Link and Kevin argue as to how they should go about defeating the Iron Knuckle, and before they even manage to inflict damage upon the armored foe, Princess Zelda is taken by the Rebonakku and Link realizes that he must fight alongside Kevin to be able to defeat it. Together, Link and Kevin fire at the Iron Knuckle, causing its horse to disappear and giving Zelda a chance to free herself. The three heroes then shoot at the Iron Knuckle one more time to finally defeat it.

In "Having a Ball", another Rebonakku confronts them while Link, Princess Zelda, Kevin, and Princess Lana are exiting the tunnel that leads to the Island Palace. Kevin tries to shoot it with his Zapper but it has no effect, so they jump out of the way and allow the Iron Knuckle to fall into a nearby lake along with its horse.

The Legend of Zelda comic
The Rebonakku from The Adventure of Link appears in the Missing in Action story of the Legend of Zelda comic, although he is only known as an Iron Knuckle. Like in the game, he is the guardian of the recorder in the Island Palace. When Link and Zelda arrive to the palace in search of the Recorder, they are confronted by the Iron Knuckle. After a grueling battle, Link defeats his foe, knocking its helmet off. It turns out that it is a human, and not a monster under the armor. The man explains that an old king charged him with protecting the  treasures within the palace, and that he was to stop anyone who was unworthy. He tells the duo that by defeating him, they are free to take what they want, and he shows them a secret wall that contains the magic flute.

Trivia

 * In the Japanese version of The Adventure of Link, Iron Knuckle's Sword Beams flash and will disappear when blocked, much like Link's own, but in the NES version, they will not flash and will bounce off of Link's shield. The Nes Game Atlas referred to these attacks as knives, rather than beams.
 * It is possible that "Rebo" in the name Rebonakku was intended to mean "Levo" as in levitate, referring to his floating horse.
 * Rebonack's steel horse is the first appearance of a horse in the series, not counting the unicorn dragon Aquamentus.
 * In Ocarina of Time, the armor within which Nabooru is encased looks slightly different than that of the other Iron Knuckles fought in the game, particularly the helmet. It also does not weild a weapon until the fight begins, instead it summons an axe from thin air by snapping its fingers.
 * Onox, the main antagonist of Oracle of Seasons, highly resembles the appearance of an Iron Knuckle. The only real difference is that Onox wields a Ball and Chain while Iron Knuckles tend to use axes.
 * Iron Knuckles from Ocarina of Time and Majora's Mask wear a cloth tunic bearing Gerudo patterns, similar to those seen on Ganondorf's and Twinrova's clothing.
 * If Link positions himself behind an Iron Knuckle and the camera is panned through its armor, the face of a Gerudo is visible through its helmet. This is most likely only used as a model for the creature but it can be theorized that Ganondorf turns his people into Iron Knuckles. This also works in Majora's Mask, and then more of the body is visible.