Sorry to reawaken this Old thread, But there is an Update on the Rust-like Cloud of the Villa.
-OWB+NV spoilers-
In Old World Blues, You find the answer to where the gas that had engulfed the villa came from.
It turns out that Sinclair, As rich as he was, Was not rich enough to pull off the massive operations he was planning to do at the Sierra Madre.
So he made a deal with the top scientists at Big Mountain, They would help fund the construction of his Villa, And in return he'd allow them to run experiments on the inhabites.
One of these experiments Sinclair was not made aware of: A malicious cloud of hazardous gas. The Scientists had been asked to create a type of chemical weapon that could be droped on Important Buildings within China, Kill all inside, but without harming the building or anything else within it.
The scientists at big mountain created such a cloud. and decided to test it deep within the vault of the Sierra Madre. The plan was to set off a small Dose of the cloud and record how it affected the workers who were building the vault. With this method they hoped by doing these experiments in the vault, It would be out of the public eye, And Sinclair would think the cloud was natural of the landscape, Instead of man-made.
Also, The scientist's wished to test our new hazard suits made specifically to protect one from the cloud. So when Sinclair called Big Mountain up, complaining about a mysterious cloud that was halting construction, The scientist's offered to loan some of these new prototype suits to a group of workers at the Sierra Madre.
The test became a Complete Disaster.
The Hazard Suits did not protect against the cloud completely. As stated. It ate away at the locks on the suit, and in the end, turned the people inside of them into Ghouls.
Before Big Mountain could get a handle on the situation, Nuclear War broke out.
As humanity fell into Chaos, The cloud went unchecked. It Began to grow, eventually leaking out of the vault into the villa. Where it killed anyone who Inhaled it in large doses.
And So that is the answer to the mystery of the Sierra Madre. A Place built by a man deep in love to protect a woman who was not faithful to him from Nuclear War which it failed to do And in the end the experiments done to the place scarred it for eternity.
P.S I'll be writing a Review for "Old World Blues" as soon as i complete it. Its by far the biggest DLC out of the 3 released so far. You find out a lot of where certain things in NV came from. I recomend getting it