Onix is a Pokémon made up of a large chain of gray boulders that gradually decrease in size towards its tail. It stands as the tallest Rock-type Pokémon due to its impressive length. This creature features black eyes and a rounded snout, with a rocky spine on top of its head. As Onix ages, its form becomes more rounded and smoother, eventually resembling black diamonds. Inside its brain lies a magnet, functioning as an internal compass to guide Onix and prevent it from getting lost while digging underground.
Onix can tunnel through the ground at speeds exceeding 50 miles (80 kilometers) per hour, causing tremors and a loud, echoing roar. Any hard objects encountered during its tunneling are absorbed into its body, making it incredibly sturdy. It also feeds on the rocks it encounters. The extensive tunnels left behind by Onix often serve as homes for Diglett. According to the Pokémon Stadium series, Onix can rotate its head or any part of its body in a full 360 degrees. Known for its aggressive nature, Onix will frequently attack humans and other Pokémon when in pain, as depicted in the anime. In the Pokémon Adventures manga, Onix has been shown to survive being separated from its body segments during battles, either regenerating or reattaching later. It is believed that an Onix living for about 100 years may evolve into Steelix once its composition becomes more diamond-like. This Pokémon can typically be found in mountains and caves.
Evolution
Onix evolves into Steelix.
(Source: Bulbapedia)
