Type: Steel/Ground
Classification: Iron Snake Pokémon
Height: 10.5m
Weight: 740kg
Ability: Sand Force
The cells within its body, crystallized by the energy produced from Mega Evolution, are stronger than any mineral and able to withstand any temperature. It moves incredibly slowly, but its strengthened body is also impervious to damage, and it lashes out at foes without flinching.
After Mega Evolving, it gains a high boost to its already high Defense stat. This ensures that it can endure hits from opponents that take the first shot, and strike back with its boosted Attack.
Its Sand Force Ability will increase the power of Rock-, Ground-, and Steel-type moves by 30% during the sandstorm weather condition. If Mega Steelix uses Iron Tail during a sandstorm, it will be able to deal heavy damage. If an opponent survives this strike, its defense will be lowered as an after-effect of the attack.
Reference and images: Serebii.net
Additional references, images, and information: pokemonrubysapphire.com