Third Kazekage

The was the leader of Sunagakure, recognised as the village's strongest Kazekage.

Background
After studying the jinchūriki of Shukaku of the time, he recreated its sand-manipulating powers by combining his own magnetic chakra and iron powder, which produced the Iron Sand technique. It was for this very ability that he was noted as the strongest Kazekage in the entire history of Sunagakure.

At some point, Sasori kidnapped and killed the Third Kazekage in order to turn him into a human puppet. According to Sasori, the effort involved in the Third's capture made it his favourite puppet. Sunagakure was not aware of what Sasori had done and searched earnestly for his whereabouts. However, with the ongoing war against Sunagakure, the village was forced to choose a Fourth Kazekage, though they still attempted to search for him in later years.

Appearance
The Third Kazekage had short messy, dark blue hair, yellow eyes, and wore the normal Kazekage attire minus the Kage hat.

Abilities
While alive, the Third was undoubtedly a powerful shinobi. He is hailed as the strongest Kazekage in the village's history, and even a very powerful shinobi like Sasori claimed that he had trouble killing him. He also appeared to have possessed a high level of intelligence as he was able to comprehend the One-Tail's unique powers and produce his own version of the same, thus creating Iron Sand.

Nature Transformation
The Third possessed the kekkei genkai Magnet Release which allowed him to convert his chakra into strong magnetic forces, enabling him to manipulate magnetic objects. Combined with his research of Shukaku's powers, he crafted his own version of "sand-manipulation", the Iron Sand, by combining his magnetic force control with iron powder; this was the main reason why he was considered the strongest Kazekage there was. His magnetic control also granted him immunity from all metallic weapons, as well as the ability to nullify opposing puppets by clogging their joints with sand. With this "sand", he could make weapons to fit various occasions, thereby making this a very versatile technique, which Chiyo considered to be the "most feared weapon in the history of Sunagakure".

Kazekage Rescue Mission
It was during the battle against Sasori did Chiyo finally realised the Third Kazekage's fate, seeing the human puppet that Sasori brought out.

Kaguya Ōtsutsuki Strikes
The Sage of the Six Paths calls upon the souls of the Third and all the other deceased Kage at the end of the Fourth Shinobi World War. The Kage combine efforts to summon the members of Team 7 and all nine tailed beasts from Kaguya's Dimensions. Once their task is complete, the Sage returns the Kage's souls to the Pure Land.

Trivia

 * Both he and the Third Mizukage are the only Kage whose names are unknown.