Blackrock Caverns is the first of two new wings in Blackrock Spire introduced in World of Warcraft: Cataclysm. It is designed as a 5-man instance for players level 35. It is a series of tunnels created by Twilight's Hammer clan in order to gather the remaining Ragnaros' minions and transport them back and forth to Mount Hyjal, as well as to perform horrific experiments conducted by the nihilistic cult in order to use the essence of the dragon in order to transform the worthy into dragonspawn. Pip Quickwit and Raz the Crazed were enlisted by the Guardians of Hyjal to investigate the activity within the caverns. The forces here are led by the Ascendant Lord Obsidius.
In the bowels of Blackrock Mountain, beneath the more traversed parts of the mountain's spire, the Twilight's Hammer puts this hope into practice. Surrounded by boiling spouts of magma and burning rock - as well as the dangerous elementals that call Blackrock home - the cult will reforge their devoted in the image of the world they work to destroy.[1]
Adventure Guide
Rumors suggest that Deathwing himself carved out the subterranean labyrinth that allows the Twilight's Hammer to secretly transport elementals from the majestic Mount Hyjal to Blackrock Mountain.
A vital hub of this shadow network is Blackrock Caverns, site of the cult's blistering forge and some of its most heinous experiments, including the transformation of cultists into twilight dragonkin.
Geography
Players need to be level 30 to use the Dungeon Finder for the instance. The entrance is just off of the main ring in Blackrock Mountain on the non-jumping path to Blackrock Spire. Head to the eastern side of the ring to see the summoning stone for Blackrock Spire and follow the path in toward that instance. As it turns north there is a blockade blocking the way. Just past the blockade, look right to see the instance entrance.
Head towards the Blackrock Spire entrance portal, and take a right. Follow the hallway and take the first left. Follow this path until there’s a fork going left down a walkway, and straight upwards. Take a right down the path (or jump, for those daredevils out there) and take another right, and, Voila. Alternatively, take the Mole Machine from Finkle.
Hotfix (2010-12-14):The Looking For Dungeon random bracket has been changed from level 80-81 to 80-82, and the specific bracket has been changed from level 80-83 to 80-85.
Hotfix (2011-12-02):Raz the Crazed's Furious Swipe should now properly hit enemies.
Ascendant Lord Obsidius
Chamber of Incineration
Twilight Forge
[30-35D] This Can Only Mean One Thing...
Pip Quickwit
Karsh Steelbender Auto Accept (Hostile)
Beauty Auto Accept (Hostile)
Ascendant Lord Obsidius Auto Accept (Hostile)
[30-35D] Dark Iron Contingency Plan
[Dwarf Rune Stone]) reduces elemental damage taken by the party by 5%.
Map of Blackrock Caverns as of BlizzCon 2009
A translucent model of a dragon in the dungeon. It was ultimately replaced with chained up nether drakes.
Hotfix (2010-12-14): The Looking For Dungeon random bracket has been changed from level 80-81 to 80-82, and the specific bracket has been changed from level 80-83 to 80-85. 
