Who are the Dark Iron Dwarves

The Dark Iron Dwarves are one of the Dwarven Clans (Ironforge, Bronzebeard, Wildhammer, Frostborn and Dark Iron). They have been ousted during a great war for their desire for conquest, and most live enslaved by the fire lord Ragnaros. They are unique among the Dwarven clans for their use of Arcane magic, predominantly of the Fire element.