Onix resembles a giant chain of gray boulders, with a rocky spine on its head. This Pokémon has a magnet in its brain that serves as an internal compass. Onix's body becomes more rounded and smoother as it grows with age. A fully-grown Onix measures at an enormous 28 feet 10 inches, or 8.8 meters.
Onix tunnel under the ground at over fifty miles per hour, which causes tremors. If they take a hard enough blow and their body falls apart, they can regrow the rest in a matter of a few weeks. They share this trait with Arbok. Onix are capable of rotating their head, or any part of their body, a full 360 degrees.
They are very hotheaded Pokémon and will constantly attack humans and Pokémon when various objects are caught in its craggy body. However, domesticated Onix will show signs of distress instead of attacking others.
Onix can be found in mountains and caves, though they prefer underground tunnels with little light. It can also be found in craggy mountains and abandoned mines. It is most common in Kanto and Johto.
Onix eats large boulders.
This Pokémon was unavailable prior to Generation I.