[[File:Brock Onix.png|As an {{p|Onix}}, battling [[Ash's Pikachu]]|left|thumb]]
[[File:Brock Onix.png|As an {{p|Onix}}, battling [[Ash's Pikachu]]|left|thumb]]
Onix was first seen during Brock's match with Ash at the [[Pewter Gym]]. It was used against {{AP|Pikachu}} and was shown to be a very powerful battler. It used a powerful {{m|Bind}} attack to subdue Pikachu and was not even fazed by Pikachu's {{m|ThunderShock}} as it's part {{t|Ground}}. This caused Ash to forfeit the match because he could not stand to see Pikachu in pain, giving Brock the victory. Onix was also used in Brock's rematch with Ash where it battled {{AP|Pikachu}} once again. This time Pikachu's newly learned {{m|Thunderbolt}} attack was actually able to cause damage to Onix. Onix tried to bind Pikachu again but Thunderbolt proved to be more powerful then Brock anticipated. However it was still not enough to defeat Onix so Brock told Onix to stop binding Pikachu because Brock did not want to hurt it. Things turned worse for Brock when Pikachu's Thunderbolt set off the sprinklers severely damaging Onix because of its weakness to water. Onix was then taken down by one final Thunderbolt by Pikachu, but Ash forfeited. Brock decided to give Ash the badge anyway, and then joined him on his adventures, bringing Onix and {{TP|Brock|Geodude}} with him.
Onix was first seen during Brock's match with Ash at the [[Pewter Gym]]. It was used against {{AP|Pikachu}} and was shown to be a very powerful battler. It used a powerful {{m|Bind}} attack to subdue Pikachu and was not even fazed by Pikachu's {{m|ThunderShock}} as it's part {{t|Ground}}. This caused Ash to forfeit the match because he could not stand to see Pikachu in pain, giving Brock the victory. Onix was also used in Brock's rematch with Ash where it battled {{AP|Pikachu}} once again. This time Pikachu's newly learned {{m|Thunderbolt}} attack was actually able to cause damage to Onix. Onix tried to bind Pikachu again but Thunderbolt proved to be more powerful than Brock anticipated. However it was still not enough to defeat Onix so Brock told Onix to stop binding Pikachu because Brock did not want to hurt it. Things turned worse for Brock when Pikachu's Thunderbolt set off the sprinklers severely damaging Onix because of its weakness to water. Onix was then taken down by one final Thunderbolt by Pikachu, but Ash forfeited. Brock decided to give Ash the badge anyway, and then joined him on his adventures, bringing Onix and {{TP|Brock|Geodude}} with him.
Onix was sent out in an attempt to prevent Team Rocket escaping with a Moon Stone in ''[[EP007|Clefairy and the Moon Stone]]''. It tunneled through ground and burst up to disrupt the escaping Team Rocket, and although it fought to a stalemate with {{TP|James|Koffing}}, it held them up long enough for Ash and the others to arrive and save the day.
Onix was sent out in an attempt to prevent Team Rocket escaping with a Moon Stone in ''[[EP007|Clefairy and the Moon Stone]]''. It tunneled through ground and burst up to disrupt the escaping Team Rocket, and although it fought to a stalemate with {{TP|James|Koffing}}, it held them up long enough for Ash and the others to arrive and save the day.
Brock's Steelix (Japanese: タケシのハガネールTakeshi's Haganeil) was the first Pokémon acquired by Brock in the anime, and is his main battling Pokémon in both the anime and games.
Brock receiving Onix on his 10th birthday in the anime
Brock received it as an Onix from his father, Flint, on his tenth birthday, as seen in a flashback in Having a Wailord of a Time. Onix was Brock's first, most powerful and signature Pokémon.
Onix was first seen during Brock's match with Ash at the Pewter Gym. It was used against Pikachu and was shown to be a very powerful battler. It used a powerful Bind attack to subdue Pikachu and was not even fazed by Pikachu's ThunderShock as it's part Ground. This caused Ash to forfeit the match because he could not stand to see Pikachu in pain, giving Brock the victory. Onix was also used in Brock's rematch with Ash where it battled Pikachu once again. This time Pikachu's newly learned Thunderbolt attack was actually able to cause damage to Onix. Onix tried to bind Pikachu again but Thunderbolt proved to be more powerful than Brock anticipated. However it was still not enough to defeat Onix so Brock told Onix to stop binding Pikachu because Brock did not want to hurt it. Things turned worse for Brock when Pikachu's Thunderbolt set off the sprinklers severely damaging Onix because of its weakness to water. Onix was then taken down by one final Thunderbolt by Pikachu, but Ash forfeited. Brock decided to give Ash the badge anyway, and then joined him on his adventures, bringing Onix and Geodude with him.
Onix was sent out in an attempt to prevent Team Rocket escaping with a Moon Stone in Clefairy and the Moon Stone. It tunneled through ground and burst up to disrupt the escaping Team Rocket, and although it fought to a stalemate with Koffing, it held them up long enough for Ash and the others to arrive and save the day.
Like most of Brock's Pokémon, Onix received very little screentime in comparison to the Pokémon of the other main characters. This may have been due to its massive size, although this came in handy when the trio were trapped in the upside down, sunken St. Anne in Pokémon Shipwreck. Onix was used as a bridge and ladder to allow the group to reach lower levels of the ship.
Onix was used as Brock's steed in The Flame Pokémon-athon!, during the big race. It managed to maintain a very good pace, keeping second behind Dario and just ahead of a farmhand on a Rhyhorn. However, when part of the race involved crossing a body of water, the two Rock-type Pokémon were unable to cross and had to withdraw. Onix was noticeably upset by this, the only time it has been shown to weep.
In Who Gets To Keep Togepi?, Brock used Onix in the four way tournament, where it went up against Meowth. It seemed to outclass the tiny Normal-type Pokémon with its powerful Rock Throw, but Meowth was extremely determined after seeing Togepi, and managed to defeat Onix by splashing it with a watering can and then using Fury Swipes.
Brock used it in To Master the Onixpected! in an attempt to restrain a giantOnix, but it was knocked back as it was at a size disadvantage, and in The Ancient Puzzle of Pokémopolis, in an attempt to restrain a giant Gengar. It was absorbed into the ancient Pokémon just like Team Rocket, the scientists and Pidgeotto but reappeared at the end of the episode.
Johto
In Poké Ball Peril, Brock decided to remain at Professor Ivy's lab in the Orange Islands, and kept Onix with him. However, when Brock returned to the group in A Tents Situation, he brought Onix with him, as revealed in Roll On, Pokémon, where it lost a battle with a powerful Donphan.
In Sick Daze, it was revealed that Brock usually polished his Geodude and Onix as part of his Breeder duties. The dubious task of polishing Brock's Onix fell to Ash, who attempted to shorten his chore through use of his Totodile's Water Gun, which caused Onix to panic and earned Ash a reprimand from Misty. It was captured by Team Rocket, but is rescued by the arrival of Brock, Golbat and TP. It then used Rock Throw to send Team Rocket blasting off.
In Control Freak!, Jessie, in possession of an ancient Queen's mask and scepter, took control of Onix, along with Geodude and Pikachu. Team Rocket then beat a hasty retreat by ordering Onix to carry them out of the underground chambers. When Team Rocket fled, Onix was freed from the influence of the scepter. In Entei At Your Own Risk, Onix comically buried Psyduck in hot sand as it collapsed in the bed to relax. It later used its large, dense body to shield the group from Team Rocket's suction.
In the Christmas special, Onix was seen having a snowball fight with the rest of the Pokémon. It was later seen being used as a sled.
Brock ended up giving Onix and two of his other Pokémon to his eldest sibling, Forrest, who took on the role of Gym Leader at Pewter City while Brock went to Hoenn. When Brock returned to the gym in Grating Spaces, Onix had evolved into a Steelix under Forrest's care. Steelix was shown to have learned Iron Tail and a powerful DragonBreath attack during its time at the gym.
Steelix made an appearance in SS025, in which it was used by Forrest in a Gym battle against Nurse Joy.
Red challenges Brock's Onix during Onix is On! in a gym battle to gain the Boulder Badge. Red uses Pika to battle (his other two partyPokémon too tired from repeated use), but it is still angry with Red for capturing it, and ignored his commands. Onix first uses Rock Throw at Pika, which caused it to become even more annoyed, and it started shocking Red instead. Brock is infuriated that the one challenger he'd hoped to go all-out on seemed to have won his way through "dumb luck." He then revealed Onix's strongest move: using its body like a torpedo to gain momentum and hit Pika with Skull Bash. Red narrowly pushes Pika out of the way, and having decided to fight for him, the Pikachu uses a powerful electric attack on Onix, breaking apart the rocks that its body is composed of. In the end, Red seemed to have gotten Pika's trust, before using the handshake he offered to electrocute him in the outskirts of Pewter City.
Brock would later use Onix to serve as a replacement bridge in the Tohjo Falls and in an exhibition match against Jasmine, where it was soundly defeated by her Steelix's higher defense.
Since The Electric Tale of Pikachu is based on the anime, Onix appears in this manga in Ash and Brock's Gym battle in Play Misty For Me. It loses the battle.
Satoshi battles Brock's Onix in Nibi City. Satoshi uses his Charmander in the battle, and tells it to chop the horn-like part of Onix's head off. Onix is then defeated, and Satoshi wins the battle.
In the TCG
Brock's Steelix was featured in the TCG multiple times. The following is a list of cards named Brock's Onix.
