Once the capital city of the Dark Iron dwarves, this volcanic labyrinth now serves as the seat of power for Ragnaros the Firelord. Ragnaros has uncovered the secret to creating life from stone and plans to build an army of unstoppable golems to aid him in conquering the whole of Blackrock Mountain. Obsessed with defeating Nefarian and his draconic minions, Ragnaros will go to any extreme to achieve final victory.Wowpedia
I bought that leather recliner, of course. Then I went home and tried it out.
For those who d0 not play the game, Blackrock Depths is the longest, largest instance in World of Warcraft. Blackrock Depths only rival on the size and difficulty scale is Sunken Temple[, which has been radically truncated in the current version of the game. Before the introduction of shortcuts into the instance, some areas within the map were 20 minutes travel away from the beginning of the instance, making wiping on the instance a disastrous consequence to be avoided at all costs].
The average time to complete the entire instance is 4–6 hours due to its complexity