Onix

Onix, known as Iwark (イワーク) in Japanese, is a dual-type Rock/Ground Pokémon introduced in Generation I. It resembles a giant serpentine creature composed of large gray boulders, with smaller rocks making up its tail. Onix has a horn on its head and small black eyes. It is known for its massive size, being one of the tallest Rock-type Pokémon. Onix possesses a magnetic brain, which allows it to maintain its sense of direction when digging tunnels. It tunnels underground at speeds of up to 50 miles per hour (80 kilometers per hour), consuming rocks and dirt. This tunneling behavior causes tremors and a terrifying roar. Onix absorbs hard objects it encounters while digging into its body, which makes it very sturdy. Its tunnels are often used as homes by other Pokémon like Diglett. Onix will constantly attack humans and other Pokémon, especially when in pain. It is said that an Onix that lives for about 100 years will evolve into Steelix after its body becomes more diamond-like. Onix typically lives in mountains and caves. On occasion, Onix is known to sleep while digging tunnels. In the Pokémon anime, Onix has made numerous appearances, most notably as Brock's Pokémon.