Blackreach (Skyrim)

Blackreach is a colossal underground cavern found under the Tower of Mzark, filled with glowing mushrooms and Falmer. The cavern encompasses the area between three Dwemer cities-- Alftand, Mzinchaleft, and Raldbthar-- and connects them.

Like all the other Dwemer cities, it now lies in ruin, overrun by Falmer, Chaurus and Glowing Mushrooms. The Glowing Mushrooms here are exponentially larger than those found elsewhere, the ceiling of the entire cave system glows with blue lights, and massive glowing vines that hang down. There is a teal fog within Blackreach that makes grasping the size of Blackreach difficult, and mushroom spores that float throughout the air. Massive geode stones and geode veins also dot the ground, and the pools of water found within are an almost entirely opaque teal.

Players normally first encounter this massive location as part of the Elder Knowledge quest, although it is possible to discover it beforehand (for more info: Discerning the Transmundane).

Sublocations
From Blackreach, one can reach the following areas:
 * Alftand Cathedral - Once cleared, the Alftand Cathedral contains an entrance to and exit from the far northeast end of Blackreach.
 * Raldbthar Deep Market - Located on the peak near Shearpoint (where you fight Krosis). Once cleared this also requires the Attunement Sphere to enter.
 * Mzinchaleft Gatehouse - Once cleared, the Mzinchaleft Gatehouse contains a Dwarven Mechanism that, once activated, opens a spiral staircase in the floor around the mechanism. You will need the Attunement Sphere to activate the Dwarven Mechanism, which can be obtained from Septimus Signus at Septimus Signus's Outpost which is north of the College of Winterhold. This leads directly to a door to Blackreach. Because the Mzinchaleft Gatehouse can be accessed quickly (once cleared) from Skyrim, using an unlocked elevator (the entrance is located on the road just northwest of Mzinchaleft), this location can be a fast, straightforward access point to Blackreach for returning players.
 * Tower of Mzark - This is the initial point of entry into Blackreach, and is the only one available until players engage in the Elder Knowledge quest.
 * Great Lift at Mzinchaleft - Located just south of Mzinchaleft. Becomes accessible and appears on the world map after it has been used for the first time to exit Blackreach.
 * Great Lift at Raldbthar - Becomes accessible and appears on the world map after it has been used for the first time to exit Blackreach.
 * Great Lift at Alftand - Becomes accessible and appears on the world map after it has been used for the first time to exit Blackreach.
 * Hall of Rumination
 * Debate Hall
 * Pumping Station (Silent City)
 * Derelict Pumphouse
 * Silent City Catacombs
 * Farm Overseer's House
 * Silent Ruin
 * War Quarters
 * Reeking Tower
 * Sinderion's Field Laboratory

Although all of the locations above are easy exits from Blackreach, these locations need to be "unlocked" as entrances. This can be accomplished, in some cases, by clearing said location and reaching a mechanism to open the entrance. In other cases the entrance must be "unlocked" by first using it as an exit out of Blackreach, after which time the entrance will be accessible for the rest of the game — some (the Great Lifts) will even appear on the map for fast travel.

Quests

 * Main Quest: Elder Knowledge
 * Daedric Quest: Discerning the Transmundane
 * Side Quest: A Return To Your Roots

Alchemy
Because of the vast size of Blackreach, these figures may not be exhaustive.
 * Bleeding Crown - 10
 * Blisterwort - 17
 * Chaurus Eggs - 32+ (Drops from the Chaurus in the area)
 * Crimson Nirnroot - 39
 * Dwarven Oil - 0+ (Drops from the Dwarven Automatons in the area)
 * Falmer Ear - 0+ (Drops from Falmer in the area)
 * Fly Amanita - 2
 * Giant's Toe - 0-1 (Drops from Giant in the area)
 * Glow Dust - 4
 * Imp Stool - 3
 * Namira's Rot - 5
 * Spider Egg - 2
 * Troll Fat - 2
 * White Cap - 4
 * Wisp Wrappings - 1

Mining

 * Corundum Ore Veins - 14
 * Ebony Ore Veins - 5
 * One between the Pumping Station and two Falmer huts, almost directly under the balcony from the pumping station, by the Wispmother.
 * One to the far south of the Debate Hall and slightly due west of the top of the Derelict Pumphouse behind the edge of the waterfall that splits on either side of the rock that has a Crimson Nirnroot sitting on the very tip.
 * Next to Sinderion's Field Laboratory.
 * North East of the Tower of Mzark, on a small island (it's not too far from the tower's structure.)
 * Far to the south of Debate Hall and east of the Tower of Mzark (try imagining a line from those two points, and right were they meet should be the Ebony Vein).
 * Geode Veins - 30
 * Gold Ore Veins - 2
 * Moonstone Ore Veins - 2
 * Orichalcum Ore Veins - 3
 * Quicksilver Ore Veins - 3

Books

 * 2920, MidYear (v6) (Skill Book - Heavy Armor) - On a table west of the War Quarters building. Table is at the top of the short set of stairs near the lever that triggers the blade trap

Notable Loot

 * Falmer Armor - in a Falmer hut to the west of the entrance leading to Raldbthar Deep Market
 * Adept level locked chest - Inside novice locked gate/room just to the west of the Raldbthar Deep Market entrance.
 * Master level locked chest - Just to the right of the Raldbthar Deep Market entrance on the wall, facing out into Blackreach.

Enemies

 * Chaurus
 * Chaurus Reaper
 * Dwarven Centurion
 * Dwarven Sphere
 * Falmer
 * Falmer Servant
 * Frost Troll
 * Frostbite Spider
 * Giant
 * Vulthuryol
 * Wisp
 * Wispmother

Trivia

 * Blackreach is perhaps the most unique location in Skyrim. First, even though it has a ceiling, it is actually considered a place outdoors. Second, the scale in Blackreach is slightly smaller than on the surface. In other words, walking 1 mile in Blackreach is the equivalent of walking 1.3 miles on the surface.
 * Blackreach contains Crimson Nirnroot. Harvesting one will start the quest A Return To Your Roots.
 * The dragon, Vulthuryol, will spawn if you use Unrelenting Force on the large yellow orb hanging above the Debate Hall.
 * Blackreach is mentioned in the book Dwemer Inquiries Vol III. On the second to last page, the author writes "The most reasonable translation ... I have managed to decipher is 'Blackest Kingdom Reaches', but I cannot imagine what that means." Also, on the sixth page of this book, the author explains that the same Dwemer phrase is found particularly on "ornate metal frames in the deepest reaches of the Strongholds Alftand, Irkgnthand and Mzinchaleft of Skyrim." Two of these Strongholds (Alftand and Mzinchaleft) connect directly to Blackreach.
 * It is recommended to enter the Blackreach with as few things in inventory as possible since it has a lot of loot to offer.
 * There are many centurion cores to collect within Blackreach. Leaving to the surface and returning after 3 days allows the centurions to respawn and be battled again.
 * There is a Falmer hut near the building you must go to for the Daedric Artifact quest that is too low for the player to enter but always has a Falmer stuck inside it. A player can glitch into the hut if, when attacking the Falmer inside the hut, does a finishing move. The player becomes stuck in the hut and must either A - revert to a last save or B - glitch out of the hut by doing a finishing move on an enemy outside or your companion o C - transform into a werewolf to be able to run out.
 * Even though Blackreach is deep underground, Vampires will find that the glowing ceiling acts the same as the sun.
 * Humans can be found in Blackreach, but they are servants of the Falmer.

Bugs

 * Sometimes when killing a certain centurion master, you will acquire his steam and have it shooting from your shoulders and arms; to reverse this, reload a save or continue on in the main story line and it should fix its self by the end of Alduin's Bane.
 * On the PS3 version, there is a glitch that will not allow crossing of the bridge to the Elder Scroll. To fix this is simple: delete your update data from game data utility, re-update the game, and it should be fixed. This also fixes the framerate drops and seems to fix most of the glitches on the PS3 version.
 * Lifts to the surface can occasionally cause the game to effectively freeze on the loading screen, barring all actions apart from quick-loading. [PC:] It can be fixed by pressing tilde (~) and waiting 5-10 sec, then press tilde again to close console. [All:] This can also be prevented entirely by temporarily disabling autosaves on traveling, and then enabling them after using the lifts.
 * On the 360 version and PS3, there is a Falmer tent near the Ralbdthar Deep Market entrance which will trap the Dragonborn inside it if it is somehow entered (as noted previously). This usually occurs when one is trying to melee attack the Falmer inside it. There does not seem to be a solution to this bug other than loading the last save, as Whirlwind Sprint, sprinting, jumping, or rolling do not seem to allow Dragonborn to leave.
 * On some occasions, it is possible to alter the weather/daylight in Blackreach by entering and exiting the gate in the north-western corner of Blackreach (follow the path up from one of the elevators).
 * Since this place is considered as "outdoors" it might happen that an courier from the Stormcloak- or Imperial-faction spawns there.