Steelix is a Steel/Ground dual type Pokemon.
It evolves from Onix during the day, while holding a(n) Metal Coat. It evolves from Onix at night, if holding a(n) Metal Coat. It evolves from Hylian Onix during the day, while holding a(n) Metal Coat. It evolves into Mega Steelix during the day, while holding a(n) Mist Stone. It evolves into Mega Steelix at night, if holding a(n) Mist Stone.
Steelix live even further underground than Onix. This Pokémon is known to dig toward the earth's core, reaching a depth of over six-tenths of a mile underground.