The story of Burning Steppes.
The Burning Steppes are a land of ash, black rock and smouldering fires south of Blackrock Mountain, and their scars come from one terrible mistake. Long ago, the Dark Iron dwarves, exiled from Ironforge after the War of the Three Hammers, turned to sorcery. Their Sorcerer-Thane Thaurissan tried to summon elementals to win the war, and instead woke Ragnaros, the Firelord, imprisoned by the titans deep in the earth. Ragnaros's arrival melted mountains and raised the volcano of Blackrock Mountain; the land to its north became the Searing Gorge, and the land to its south became these steppes.
Blackrock Mountain has had many masters since. The orcs took its spire during the First War and made it the Horde's stronghold, and at its foot Orgrim Doomhammer struck down Anduin Lothar late in the Second War. Today the mountain is a nest of enemies: the Dark Irons rule the depths under their emperor, Ragnaros burns in the Molten Core below, and in Blackrock Spire, Rend Blackhand's orcs serve the black dragon Nefarian, who schemes from his lair at its peak. Blackrock orcs still mine the hills around it.
Only small footholds hold out against them. The Alliance's Morgan's Militia holds the ruins of Morgan's Vigil in the south-east, the Horde keeps a small outpost at Flame Crest in the north, and the Thorium Brotherhood, Dark Irons who broke with their emperor, keeps its own camp in the middle of the steppes.
Written for this site from the game's lore. Further reading: Burning Steppes on Warcraft Wiki.

