The Oxidda Chain of mountains is a mountain range on Mirrodin where the Great Furnace belches out steam and molten metal constantly. The goblins there worship it as the creator of Mirrodin, and constantly feed the Furnace both flesh and metal in order to keep it going. Even here, there are secrets within secrets; something caused the goblin elders to ostracize the rebellious Krark Clan, but no one except them knows what. Perhaps it has something to do with the ultimate origins of Mirrodin, and the hands that could be shaping it.
Mountain chains on Mirrodin replace the typical dry rocky peaks with hammered metal and twisting ductwork. The mountains are composed of metal, mostly rusted iron, scrap metal piled high, combined with structures of pipe and plate. These form peaks where Mirrodin's goblins -- and many other heat-happy creatures -- live. The mountain ranges also generate strong magnetic fields which cause anti-gravity anomalies. Metallic boulders sometimes float magnetically above the peaks.
After the Phyrexians conquered Mirrodin, Urabrask encouraged the development of a wide variety of predators and territorial constructs to prowl the Oxidda Mountains. These creatures are morphologically divergent from the Phyrexians in the furnaces; they vaguely ape the forms of Mirran life before the taking of the surface. This deployment of monstrous, animalistic creations around Oxidda is no folly for Urabrask—these creatures kill indiscriminately but don't kill each other. In other words, they serve as intrusion countermeasures. They protect Kuldotha from Phyrexians of other factions and enable the furnace-dwellers to come and go as they please between the surface and Furnace Layer.