Iron Giant

The Iron Giant is a legendary robot that attacked Mary Geoise 200 years ago. It was originally created 900 years ago, around the time of the Void Century. It is currently inactive due to running out of energy, and is kept on Egghead.

Appearance
The Iron Giant is a robot around as tall as the Ancient Giants. It wears a horned helmet, and its face and lower body are covered by grills with vertical bars.

Abilities and Powers
The full extent of its abilities is currently unknown as it ran out of energy before causing damage. However, it was able to climb the Red Line and was considered to be far beyond the scientific knowledge of the time. It later served as inspiration for Vegapunk's Vegaforce-01, however, he was unable to replicate the power source of the Iron Giant.

Luffy determined that it is supposed to move autonomously, as he could not find a place for people to pilot it from the inside.

Weapons
It is shown to be wielding a polearm of some sort during its attack on Mary Geoise.

Past
The Iron Giant was originally created around 900 years ago. 200 years ago, it suddenly appeared out of nowhere and attacked Mary Geoise, but ran out of energy before causing damage. The World Government subsequently ordered a group of scientists to destroy it, but they chose to hide it instead to study it in secret. It eventually fell into the hands of Vegapunk.

Egghead Arc
The Iron Giant was accidentally discovered by Luffy, Chopper, Jinbe and Bonney during their stay on Egghead. Luffy attempted to climb inside the robot but was unable to, determining that it was the type that moved by itself. They were then interrupted by Vegapunk who warped into the room, and later explained the history of the Iron Giant.

Trivia

 * During their attempts to get the Iron Giant to move, Luffy and Chopper try calling it by the names Robonosuke (ロボの助) and Roboking (ロボキング).
 * Robin mentions that 200 years ago was also the year discrimination against Fish-Men became an issue, suggesting it may be connected to the Iron Giant.