Registeel is a large robotic Pokémon. Most of Registeel's body is spherical and gray while the middle of its face has the appearance of being exposed as it shows black "skin" and is surrounded by raised metal. Registeel's lower half is disc-like in shape and has two cylindrical legs without toes. Its face consists of seven red dots in a hexagonal formation, and it has black arms with three fingers each that are connected to its upper half by gray hemispherical shoulders. The backs of its hands have three red triangles pointing away from the fingers.
While Registeel has been classified as a Steel-typePokémon, its body is hollow and made of a material that is harder than any known metal. However, this material stretches and shrinks despite its hardness. While one Pokédex entry noted that the material that forms Registeel's body is extraterrestrial, it is also theorized that Registeel was actually born inside the Pokémon world's mantle, before emerging onto the surface 10,000 years ago. Further evidence supporting this theory is the fact that Registeel's body was tempered by pressure underground over thousands of years; as a result, it cannot be scratched. Another theory posits that Registeel was created by Regigigas out of magma. It is unknown what Registeel can eat. It was sealed away in ruins by people during ancient times.
Brandon used Registeel first in his battle with Emerald, where it squared off against the Hitmonchan the boy borrowed from Crystal. Though Registeel took considerable damage from the accumulation of many Fire Punches and was eventually beaten by a strong Sky Uppercut attack, it managed to cause its opponent to faint as well with a clever Toxic maneuver.
Registeel appears as an occasional stage hazard in the Ironworks Chamber of the Kalos Pokémon League stage. Appearing rarely, it will use Stomp to dislodge the swords embedded in the stage, causing them to fly upwards and damage fighters. Grounded characters will also take damage from Stomp.
This Steel-type Pokémon's hollow body is made out of an ultrahard metal, forged under pressure over thousands of years underground. It can appear in the Kalos Pokémon League stage, in the Elite Four's Steel-type chamber. Its Stomp attack will launch fighters on the ground, and even the giant swords mounted on the stage!
In the international versions of Ruby, Sapphire, and Emerald, there is an unobtainable Registeel Doll programmed into the game. It was unlockable with the Japan-exclusive Regi-Dolls Decoration sete-Reader card.
Registeel may be based on the golems of Hebrew legend. The legends cast them as servants of higher powers and are said to have writing on their heads. When the writing is removed, the creature would be weakened, or even killed in some legends. Given its metallic construction, it may also be based on a humanoid robot.
The five Legendary titans may be collectively themed after historical epochs, with Registeel representing the Iron Age.
Registeel may be a combination of regis (Latin for royal) and steel.