Steelix (the Iron Snake Pokemon) is a rare Steel/Ground-type Pokemon found among dark caverns within the Kanto, Johto, Sinnoh and Unova regions. Devastatingly durable and extremely difficult to overcome with physical strength alone, Steelix are monstrous creatures that easily take the notion of defensive battling to a whole new level of pain and suffering. They might be unbelievably slow and difficult to use properly in battle for sheer offense, but if you need an impenetrable wall on your side, few Steel-types can do the job as well as these metallic snakes; just make sure not to get too close to them in battle, less you find out just how much worse this beast's bite is when compared to its bark!
When Onix have lived for so long that their bodies become rounded in appearance, they move deep underground and stay in a deep burrow for several years, allowing their bodies to become tempered by intense heat and pressure. During this time, accumulated metal compounds obtained from swallowing large amounts of soil begin to rise to the surface of their stony bodies and precipitate outward via solid state diffusion, forming a thick and highly reflective metal coat over every single portion of their bodies. By the time their entire bodies are covered, Onix have become so radically changed in terms of both structure and abilities that they can officially be considered to be Steelix; if time is an issue, however, this same slow evolution can be obtained at an accelerated rate by exposing Onix to certain energy fields (such as those found in trading devices) while they are holding a Metal Coat item. The addition of heavy metal on the outside of their bodies slows these creatures down considerably and makes it much more difficult for them to move their bodies around freely; this issue is only enhanced by the metallic spires that sprout off the sides of their body during the evolution process (which are actually designed to enable digging through rock material that is even too hard for Onix to handle). On the other hand, however, it also substantially increases the physical defense of these creatures (not surprising considering that the metal covering their bodies is harder than diamond) and amplifies both the amount of physical damage they are capable of dealing and the amount of overall damage they are capable of taking, so the drop in mobility is more than compensated for.
Much as with Onix, Steelix move through rock and soil by squirming and wriggling their bodies rapidly and harshly, leaving burrows that are then occupied by subterranean Pokemon; the only difference is that the tempered bodies of Steelix allow them to travel to much greater depths than their pre-evolved form, sometimes as deep as six-tenths of a mile underground. It is here that Steelix find the most appetizing of boulders, which they gladly devour with their massive and incredibly strong jaws. Unlike Onix, Steelix are unable to utilize the many Rock-type attacks they learn naturally to the best of effectiveness and do not learn any strong offense Steel-type attacks aside from Iron Tail; as compensation, they have come to rely on their imposing jaws to attack opponents in close quarters. The jaws of Steelix are actually capable of crushing cars and thick stone like crackers, granting them a devastating Crunch attack (which they learn in place of their pre-evolved form's Sand Tomb attack) practically guaranteed to smash through thick armor with little trouble. In addition, exposure to rare Earth metals with unique physical and chemical properties naturally allows these beasts to utilize the Fire Fang, Ice Fang and Thunder Fang attacks to great effect in battle. In short, it is a very unwise idea to ever go near a Steelix, let alone challenge it to a battle, without a strong selection of special attacks and a significant mobility advantage, traits that are unfortunately less than common among Pokemon with a type advantage against these creatures.
Though they might not be among the fastest of fighters in any given battle, Steelix are mobile juggernauts capable of withstanding physical blow after physical blow while dishing out massive damage with attacks like Iron Tail and Crunch. With the highest base Defense stat out of all Steel and Ground-type Pokemon and a massive assortment of punishing attacks, it come as no surprise that Steelix are considered to be among the most powerful of defensive fighters known to exist. Bring your best special attacks to bear when fighting these creatures and do your best not to let up at any given moment; otherwise, there won't be much out there capable of stopping these iron giants from squeezing and devouring your Pokemon like they were just another rock!