Rebonack

Rebonack is the boss of the Island Palace in The Adventure of Link. He is a powerful blue Iron Knuckle mounted on a floating mechanical horse and wielding a jousting lance. Two others are later encountered in the Three-Eye Rock Palace as mini-bosses.

Strategy
While mounted on his horse, Rebonack retreats off or almost off screen, then charges at Link at high speed. Seemingly on the back foot against a mounted opponent, Link must move to the middle of the room and when Rebonack charges, jump and use the Down Thrust to damage him.

After he has suffered enough damage, his horse will run away, Rebonack leave his lance, draws his sword and will fight Link on foot as a standard Blue Iron Knuckle by shooting Sword Beams. However, Rebonack has two unique capacities. He is much better defender than any Iron Knuckles and he can back off the screen where Link can't follow him and can keep shooting Sword Beams at Link while doing so. During the second phase, the best is to bait him to the middle of the room repeatedly.

Captain N: The Game Master
Rebonack 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 Rebonack reveals himself to be the guardian of the potion. Link and Kevin argue as to how they should go about defeating him, and before they even manage to inflict damage upon the armored foe, Princess Zelda is taken by Rebonack and Link realizes that he must fight alongside Kevin to be able to defeat it. Together, Link and Kevin fire at Rebonack, causing its horse to disappear and giving Zelda a chance to free herself. The three heroes then shoot at him one more time to finally defeat it.

In "Having a Ball", another Rebonack 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 Rebonack to fall into a nearby lake along with its horse.

The Legend of Zelda comic
Rebonack 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 Rebonack. 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

 * It is possible that "Rebo" in the name Rebonack was intended to mean "Levo" as in levitate, referring to his floating mechanical horse.
 * Rebonack's mechanical horse is the first appearance of a horse in the series, not counting the unicorn dragon Aquamentus.
 * In the Japanese version of The Adventure of Link, one Rebonack in the Palace on the Sea was replaced by a Horsehead.