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The Cloud.jpg
The Cloud is what blankets the sky here... you may smell it in the air, copper and sulfur... burns the lungs and seeps into the skin.Father Elijah

The Cloud is an airborne toxin, spewed over the dead city of the Sierra Madre by the air conditioning and climate control systems inside the Sierra Madre Casino & Resort. Over the years, the Cloud has only grown into a massive blood-red fog that blankets the entire Sierra Madre.[1]


Created as an experiment by the Big MT execs, the Cloud is a product of the Z-43 innovative toxins plant located in the crater. When Frederick Sinclair came to Big MT for technology to purchase for the Sierra Madre, he unwittingly signed a Faustian pact: Apart from holograms and matter recombinators, the Think Tank would also place the Cloud at the Sierra Madre, using the casino, villa and its inhabitants as guinea pigs in its experiments.[2] Sinclair likely saw no other way to get the technology he needed, as he was already teetering on the brink of bankruptcy when he started negotiating with the executives. Of course, he was not informed that he would be receiving more than just harmless prototypes.[3] The Sierra Madre was the only testing ground that was protected by the Cloud, which was hardly a prize.[4]

The Cloud manifested itself for the first time when the cheap villa ventilation system ground to a halt, a victim of cutting corners and Mr. Yesterday's dubious practices. The pipes backed up, spewing out the red cloud. Workers in the area started choking and vomiting. Hospitalized in the villa clinic, the damage to their health was extensive enough to put them out of commission for good.[5]

To deal with the problem, Sinclair negotiated with the Big MT executives for yet another technology: The Darklight hazmat suits.[2] Although considered creepy by the maintenance crews, they allowed the crews to explore the ventilation system and try, in vain, to identify the source of the Cloud.[6]

The teams managed to find the source of the problem in the main ventilation pipe. However, traces of the dust cloud were present and eroded the metal of the suit's locks, exposing them to the Cloud and sealing them within.[7] The crewmen retreated and headed to the villa clinic to get medical attention. Much to the displeasure of the attending physicians, they cut themselves out of the suits with steak knives.[8][9]

However, despite the problems, the ventilation system was eventually restored to barely functional order. When the Great War hit shortly afterward, it continued to work for a few more years, before finally giving up the ghost. The Cloud gradually seeped into the area, climbing out of the damaged vents, eventually blanketing the area, blotting out the sun.[10][11] It became a grim, uncompromising guardian of its secrets. The maintenance crews who donned their hazmat suits and tried to fight it, succumbed to its effects, mutating and becoming the violent, savage guardians of the Sierra Madre.[12]

For centuries, the Cloud protected the casino and the villa, killing scavengers or weakening them so that they would become another victim of the tribe inhabiting it, the hazmat suited ghost people. It wasn't until the 23rd century that it became important once more. Father Elijah, a disgraced Brotherhood of Steel elder, learned of its existence from Ulysses. It inspired him.[13] When preliminary samples taken from air on the edges of the Sierra Madre yielded promising results, he set up a chemistry set to allow it to replenish itself and traveled to the Madre in person, to perform research onsite.[14]

Upon further research, Elijah decided to weaponize the Cloud as a weapon of mass destruction, to wipe the slate clean. It was intended to be used to reclaim the Mojave and destroy the New California Republic. He also plans to use it as an offensive technology, unleashing it upon the Mojave, cutting it off from the rest of the world. He could then use modified REPCONN rockets to push out both the New California Republic and Caesar's Legion at Hoover Dam, and finally, let traces of it drift west to NCR territory.[15][16][17]


The alloy that makes up the Pre-War kitchen knives is unknown, and seems to have decayed in contact with the toxic cloud.Loading screen

The Cloud is a self-replicating[14] airborne toxin that's poisonous to living beings that causes a noticeable burning sensation in the lungs and can even enter the body through the skin.[18] It is blood red in color,[19] with the consistency of a dust cloud.[5] It smells of copper, Old World gold,[20] with a tinge of sulfur.[18]

The Cloud can be corraled and dispersed through the use of fans. Parts of the Cloud can be dispersed in the streets of Puesta del Sol by reactivating the ventilation fans. Most of the Cloud in Salida del Sol South can also be cleared.[21]

The lethal dose depends on the concentration. People outside sheltered locations in the Sierra Madre are exposed to low concentrations of the toxin. The effects include trouble with eye focus, dizziness, coughing fits,[22] choking, vomiting[5] and general deterioration of health as the toxins enter the system through the lungs and the skin. Unless the victim treats the damage or leaves the area, exposure is eventually lethal. For this reason, sleeping outside is a death sentence.[23][24][25]

Concentrated pockets of the Cloud are outright lethal as they directly attack the body and cause necrosis (decay). While some can survive the concentrations of the cloud for some time, if healthy enough, none can withstand its effects for long. This is made worse by the fact that there is no protection against the Cloud. Rebreathers, chemical suits and other means of protection are useless as they fail when faced by the Cloud.[26] As damaging as the Cloud is to living beings, it preserves dead matter almost perfectly. Well built structures can last centuries intact.[27]

One effect of the Cloud is the effect it has on people wearing the Darklight hazmat suits. While outright exposure to the Cloud kills, when filtered through the suits, it apparently changes the physiology of the victim, mutating them into something else. These ghost people stalk the Sierra Madre, still wearing their hazmat suits, and are extremely tough to kill. Damage can render them inert, but the Cloud outside and that trapped within their bodies, in pockets,[28] will eventually regenerate them. Only destroying their limbs, head or destroying the body entirely (disintegration, molecular destabilization, etc.) will permanently kill them.[29]

The Cloud's concentrations can be fashioned into consumables.[30] When boiled and distilled into a liquid form, mixed with pre-War potato chips, it becomes a disgusting concoction that has an invigorating effect.[31]

Gameplay effects

When the player character enters a pocket of toxic Cloud concentration, their vision gets altered after one second, then the Cloud starts dealing 2.5% base health damage every 0.25 seconds - or effectively 10% base health damage every second - until the Cloud is left again.

In Hardcore mode, the Cloud slowly poisons the player character at outdoor locations of the Sierra Madre, dealing three health damage every 20 seconds. This will not occur in indoor locations or if the player is below 10 Hit Points.

Dean Domino's Unclean Living perk gives you 5 seconds before taking damage and reduces that damage by 25%, but prolonged stay is still not advisable. Completing the add-on will also remove the health deterioration in Hardcore mode, though concentrated pockets of the cloud will still poison the player character.

Large concentrations of the Cloud block off areas of Puesta del Sol and Salida del Sol. The former can be cleansed at the Puesta del Sol switching station during Mixed Signals. The latter area can be cleared by using the terminal near Dog's position and resetting the fans.

Cloud residue can also be collected and fashioned into consumables by the player character. Dean Domino can teach the player character how to create the aforementioned Sierra Madre martini, adding to the Ghost Sight recipe they have with Survival 25. It can also be used to create different types of toxins to use against enemies.

At the right of the entrance to the switching station in Salida del Sol South, where Dog/God is stationed to discharge the fireworks for the Gala Event, there is a monitor used if necessary to lock Dog/God in the switching station. If this monitor is activated after the conclusion of Dead Money, it will show three sub-menus: Substation Status, Ventilation System Status and Reset Ventilation System. Clicking on Ventilation System Status will bring up a display that indicates that two of the five main fans for Salida del Sol South, Fan 2 and Fan 5, are offline and need to be reset. This can be done via the Reset Ventilation System link on the main screen, and then all five fans are shown as back online, and the Cloud in the streets of Salida del Sol South disperses (though it remains in pockets in some rooms, and the area outside the neighborhood is unaffected).


  • The rebreather, space suit, radiation suits, or any power armor will offer no protection from the Cloud.
  • The Cloud is able to decay even Saturnite.
  • Upon the completion of Heist of the Centuries, the Cloud's presence is significantly diminished, allowing further exploration of the Sierra Madre without the constant drain on health. The high concentration toxic clouds, however, will still poison the player character and it is still not possible to sleep in beds that are exposed to the outside air.
  • While Dean Domino is a companion, one will gain the Unclean Living perk, which grants a short period of time (delay five seconds by default) before taking damage inside a toxic cloud as well as reducing the amount of damage taken inside the toxic cloud by 25%. This does not reduce the continuous damage applied in Hardcore mode.
  • Having the Heartless perk will not reduce the amount of damage taken while in the Cloud, even though it states that the player character cannot be poisoned. This is because the Cloud is corrosive as opposed to poisonous.
  • The default damage of the Cloud is 3 HP per 20 seconds; the toxic Cloud deals default damage of 40 HP per second.
  • The Monocyte Breeder implant can effectively offset 2/3rds of the continuous damage suffered from the cloud in Hardcore mode.
  • Due to the corrosive nature of the Cloud, the Courier cannot wait, sleep or fast-travel in the outside areas. However, it is possible to wait and sleep indoors where the Cloud does not have a strong presence.


The Cloud appears in the Fallout: New Vegas add-on Dead Money and is mentioned in a Y-17 medical facility terminal in Old World Blues.



  1. The Courier: "Could I find my way back?"
    God: "Maybe. Not sure you could find way back once leave. Dog has to smell and hunt for path back here sometimes... Cloud keep moving. It okay... no one ever leave except Dog... and Dog not want to leave. You here until Master lets you go."
    (Dog and God's dialogue)
  2. 2.0 2.1 Z-43 Innovative Toxins plant terminals, terminal, Requisition Order: Chemical Suits
  3. Y-0 research center terminals, terminal, Dispenser Funding Update
  4. The Courier: "I don't understand how an Old World casino helps you do any of that."
    Elijah: "The Cloud is unique in my travels. Its proximity to the Sierra Madre isn't a coincidence. Right now it protects this casino, preserves it. It can be used to preserve other Old World relics - and cleanse them, at the same time. And as much as I've researched hologram technology, the Big Empty facility was clear - only the Sierra Madre got Holograms working... properly."
    (Elijah's dialogue)
  5. 5.0 5.1 5.2 Puesta del Sol switching station terminals, terminal, Status Report
  6. Puesta del Sol switching station terminals, terminal, Suits are here
  7. Puesta del Sol switching station terminals, terminal, Maintenance Report
  8. Puesta del Sol switching station terminals, terminal, Suit Damage
  9. Villa clinic terminals, terminal, Safety Suits
  10. The Courier: "Tell me about the Cloud."
    Dean Domino: "The Cloud? Showed up after the Bomb. I think. I got used to it in small doses. Now, it covers the city. Over the years, it kept climbing up out of the Sierra Madre, until it was curtains for the sun. Didn't see the sky again. Doesn't seem to bother the Ghost People. Can't see through it too well, though, so sometimes I can use the Cloud for cover... if I get desperate."
    (Dean Domino's dialogue)
  11. Dean Domino: "Cloud wasn't always here. Grew over the years, even without cars or factories."
    (Dean Domino's dialogue)
  12. Salida del Sol terminals, terminal, Infrastructure
  13. Little Yangtze terminals, Little Yangtze log terminal, Elijah's Journal - Day 3
  14. 14.0 14.1 Abandoned Brotherhood of Steel bunker terminals, terminal, Science Entry 112
  15. Elijah win ending of Dead Money
  16. The Courier: "I can't argue that."
    Elijah: "Sources of food, supplies... medical assistance, ammo... make more collars, even print currency. Make a nation. The Cloud allows me to wipe the slate clean. Collars ensure cooperation. Holograms - defense. The Vending Machines provide... everything else. The Sierra Madre can kill nations and build them, using its technology with the right applications."
    (Elijah's dialogue)
  17. The Courier: "You want to attack NCR? All of NCR?"
    Elijah: "Attack? No, not attack them. Wipe the slate clean. Make the Mojave like it was meant to be... undisturbed by man. I'll send the Cloud, the Holograms. Bring ruin in my hands until only I stand atop the HELIOS One tower again. I'll scour Hoover Dam with the Cloud, rain its walls with spears from the sun... with an army of Old World ghosts behind me, Holograms all. I'll kill them until it's only me, me alone... in a quiet world. In a world that's nothing like what happened at HELIOS One."
    (Elijah's dialogue)
  18. 18.0 18.1 The Courier: "What is the Cloud?"
    Elijah: "The Cloud is what blankets the sky here... you may smell it in the air, copper and sulfur... burns the lungs and seeps into the skin. As for its origins... I am not certain. Pre-War industrial pollutants... something in the Sierra Madre structure... It is unique across the wasteland... and deadly. It has kept this place preserved since the Great War."
    (Elijah's dialogue)
  19. Dead Money intro
  20. God: "Air tastes like copper. Or Old World gold."
    (Dog and God's dialogue)
  21. Mixed Signals
  22. Elijah: "Damn Cloud still in my lungs, rattling around."
    (Elijah's dialogue)
  23. Elijah: "Outside, you may notice your vision'll pulse, get dizzy. It's the Cloud. Eats your insides, slowly. Too much exposure, death."
    (Elijah's dialogue) Note: NVDLC01ElijahBarkCloud
  24. The Courier: "What is the Cloud?"
    Elijah: "It is the Cloud covering the Villa. The longer you are outside, the more its toxins seep into your system... through the lungs and the skin. It will eat at you the longer you are outside... so wherever you go, move fast, or you'll soon find yourself too weak to move."
    The Courier: "Why is my vision blurring?"
    Elijah: "It is the Cloud that surrounds the Villa. It shouldn't prove lethal in the time you are here... prolonged exposure would be hazardous, however. Fall asleep... and you will not wake up."
    (Elijah's dialogue)
  25. Villa clinic terminals, terminal, Gas Leak
  26. The Courier: "Will exposure kill me?"
    Elijah: "No... while it will erode your health, it will only bring you to the point of death, no farther. At that point... The air here is lethal only if you enter concentrated pockets of the Cloud. Too long inside one, you'll die, so be careful where you step. I've seen some survive concentration of the Cloud for short periods of time if healthy enough - others were too weak. Rebreathers, chemical suits... there is no protection against it, it decays all it touches. I've found fighting it useless."
    (Elijah's dialogue)
  27. The Courier: "Is there any place safe to rest?"
    Elijah: "Anywhere sheltered from the Cloud... inside buildings, tunnels... any place not exposed to the outside air. Anything the Cloud has touched has preserved it one way or another... but only the Holograms in the Villa truly remain."
    (Elijah's dialogue)
  28. The Courier: "Do you know how the Ghost People taste?"
    Dog: "Taste like plastic and copper. Gas inside, in pockets, hssss when teeth sinks into them."
    (Dog and God's dialogue)
  29. The Courier: "Is there anyone alive around here?"
    Elijah: "Yes... the inhabitants... avoid them if you can, they are difficult to kill. Whatever has created them, bullets, explosions, energy... it can make them inert for a time, then they seem to crawl back up, restored. Perhaps it's the Cloud... perhaps something in their physiology."
    (Elijah's dialogue)
  30. The Courier: "What do you mean?"
    Elijah: "This place is well-preserved. Few who came here ever returned. All of the treasures of the Old World lie scattered about, virtually untouched. Search, hunt... craft what you can from what you find. The trash of the Pre-War era can keep you alive - food, knives, more. Use them. Even the Villa's toxins... and the residue it leaves behind... can be shaped into tools and weapons. Gather it as well. Also... there is one more thing in your possession, a rifle that will keep you alive, as surely as the collar will."
    (Elijah's dialogue)
  31. The Courier: "Scrounge supplies? Like what?"
    Dean Domino: "I still need to eat. At least I think I do. The Villa provides... even if it's not as glamorous as the Cantina Madrid. Once I... well, realized what you could scrounge up around here, I had a lot of time to experiment. Not the best chef, but... ...well, here's the mix, if you can stomach it. I call it a "Sierra Madre Martini.""
    The Courier: "How do you make it?"
    Dean Domino: "Scrape some Cloud Residue off the walls, mash it in a Tin Can with some Junk Food from the machines, then hold your nose and down it. There's Electric Hot Plates around if you can't find a campfire to mix it at. Also, there's other recipes you can do with the Cloud Residue... ...although it might take a hardier survivalist than me to brew them. I stick to martinis."
    (Dean Domino's dialogue)