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Steelix, The Iron Snake Pokémon. It's body has been compressed underground for years. As a result, it is harder that Diamond. It is said that if an Onix lives for over 100 years, it's composition changes to become diamond like. The many small metal particles that cover it's body reflect bright light. It lives further underground than Onix, it has been known to dig towards the earth's core.
Type: Steel/Ground

Height: 30'02''
Weight: 881.8lbs

Ability: Sturdy/Rock Head
Evolution Chain: -------Trade Whiles Holding Metal Coat------->

Location in Games:

Ruby/Sapphire: Not Avalible
FireRed/LeafGreed: Evolve Onix
Colossem: Not Avalible
Emerald: Not Avalible

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Battle Strategies:

Battle with Steelix:

Holding: Leftovers
-Toxic
-Protect
-Earthquake
-Rock Slide

Steelix has one of the best base stats in defense in the game. This pokemon can take alot of physical hits and its attack isn't too bad either. The item, Leftovers will prove useful on this pokemon since it will be able to take hits and Leftovers will heal some of the HP lost. For a nature on Steelix, I would advice either Adamant or Impish. While Adamant benefits attack but hinders special attack, Impish increases Def and reduces special attack, personally, I would pick Impish. The EV's on this pokemon is intended to increase the pokemon's ability to stay in the game. With poor special defense this pokemon wouldn't last a fire attack. For its ability, rock head is useless here since it doesn't have a move that gives any recoil damage. Its other ability, Sturdy, is pretty useless unless your opponent has One hit Knock out moves, which should be rare. If you think your opponent could possibly switch out for a pokemon with a fire type move or is a fire type pokemon, use toxic and if you feel you have a chance to survive a fire attack, attack with either earthquake or Rock slide. Otherwise, if you don't feel you have the chance to survive the attack, switch for another pokemon.

Battle Against Steelix:

Steelix has the Best Defence after Shuckle, so attacking it physical would be stupid. But it has weak SP.DEF so a volley Fire or Water Attack should take it down.

Contest Strategy:

Holding: Yellow Scarf
-Sandstorm
-Earthquake
-Tackle
-Harden

Do this, and you will have few problemes.
1: Harden 
2: Earthquake
3: Sandstorm
4: Tackle
5: Earthquake

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