As I mentioned in my last post, Blackrock Depths is located deep under Blackrock Mountain, and is the home base for the Dark Iron Dwarves, who are up to all kinds of villainy above the surface, including the enslavement of other dwarves to obtain ore to fuel their military operations, and sabotaging the massive dam in Loch Modan. Blackrock Depths was also one of the dungeons used in the original endgame to develop storylines that led into the 40-player raids, the other being Blackrock Spire. As you travel through Blackrock Depths, you discover that the Dark Irons are under the control of the powerful fire elemental Ragnaros, who dwells inside Molten Core, and is threatening to erupt from Blackrock to wreak havoc.
Blackrock Depths is massive, literally an underground city, and has many paths, as evidenced by this handy flowchart:
Rather than try to summarize all of the goings-on in BRD, I'll just hit bullet points. When you first enter, you have a choice of paths to take. The first will take you into the jail, where the Dark Irons are keeping prisoners of interest.
The prisoners' ultimate fate lies in the Ring of the Law, where they are made to fight waves of monsters, beasts and mini-bosses, including giant spiders, worgen, or a giant troll.
Another wing of the city houses the Dark Iron Armory, where you can see Dark Iron forces massing for invasion, and crafting their massive stone and iron golems.
Beneath the city flows a river of lava, which leads to the Molten Bridge, and the entrance portal to Molten Core. Knowing that players would tire of hiking all the way through Blackrock Depths just to get into the raid instance, an attunement feature was implemented, which required players to make the full trip just once, and after completing it, allowing them to get into Molten Core by simply speaking to an NPC who stood outside.
Some of Ragnaros' most intimidating minions are the large lava giants, several of which serve as bosses in Blackrock Depths. In Molten Core, they are relegated to patrol duty.The city portion of BRD has all the conveniences of a modern metropolis, including a bank...
and a fully functioning bar, the Grim Guzzler.
To reach the leader of the Dark Irons, you need to get through the military wing, which features the Lyceum, a massive deathtrap of a room where you must keep moving through a gauntlet of enemies as flames appear around you.
The final room, the Imperial Seat, is the home of the Dark Iron Emperor Dagran Thaurassian, and his queen, Moira Bronzebeard. In the original lore, Moira, the daughter of the King of Ironforge, was kidnapped, but that has since been changed to her going willingly with him. In a bit of a time paradox, Moira currently appears in both Ironforge as one of the triumvirate of rulers, mourning Dagran's death, and in BRD, with Dagran alive.