Brock's Steelix

Forrest's Steelix is one of Brock's old Pokémon he caught as an Onix in Kanto. It evolved into Steelix (not shown) and was discovered in Battle Frontier series. Steelix was given to Brock's brother, Forrest, the next Pewter City Gym Leader. It still resides with Forrest in the Pewter Gym.