People who hunt down vaults and otherwise sealed buildings are simply called prospectors in the fallout world. they specialize in breaking into sealed old world military instillation. this can be affirmed by every game, you normally find a few prospectors in every underground bunker, military instillation, or vault you go to. normally they are rather deep in the area signaling they did indeed make it quite far, but the baddie around the corner got them. sometimes those baddies are crazed vault dwellers, and lets just say a slasher/rocket junkie wearing a pipboy 3000 series is a true and immediate threat even if they appear to be unarmed. most prospectors are whittled down over the course of their "digs" as they call them and can be attributed to why the player character never encounters any real true resistance inside the vaults (vault 13 being the acceptation to this rule... deathclaws aren't very good house keepers or hosts. fuzzy deathclaws not withstanding.) The Prospectors always deal with the full brunt of an area's hostile forces leaving player characters to deal with maybe a 3rd of what used to be there. 

many prospectors die because they simply cram too much stuff in their backpack and find themselves overburdened with weight, so escaping the vault/military instillation gets them in the end. 



Also scary thing about deathclaws. They have the ability to parrot speech. yes, they can sound like a wounded traveler, or a merchant out on a caravan ride who got separated from his guards, drawing in more potential prey to an area before they strike. they can sound like children crying and calling for help. Deathclaws aren't just big, hard to kill, and have long claws that can reduce even armored troopers to giblits in a single pounce, they're also cunning and highly intelligent. The player always seems to run into deathclaws when they are NOT hunting. they always run into them when they're just milling around minding their own business. When they are hunting though that's been recorded in logs as being an entirely different story, one truly worthy of all of the nightmarish tales of them combined. These are creatures who can leap several meters in the air at great speed, tear through power armor with their claws alone, and depending on their diet, dormant genes can become active again! Deathclaws are Genetically engineered bioweapons from pre war times using a chameleon as the starting point. If a deathclaw starts to dine heavily on nightstalkers (who naturally thanks to BIG MT generate their own stealth field and were also designed as bioweapons for troops to use like a K9 unit.) they can get their camouflage genes working again, mutating the ability within a couple of months of concentrated diet. You can tell what a deathclaw has been eating by it's size, color patterns, what type of horns it has, and even the spines on it's back. What's worse? they're a byproduct from the FEV so they are entirely immune to radiation. Radiation just makes them bigger and speeds up their mutation process. If you want to know how scary they can get, Look to the Matriarch for all of your examples. This is a deathclaw who convinces a brotherhood of steel elder to allow her and her pack to join the brotherhood. And given that bethesda has said that yes, these events are cannon, you can bet everyone in the Chicago area, suddenly decided, "yeah, we're not fucking with the brotherhood anymore. taking on dudes with power armor and big guns is one thing, taking on dudes with power armor backed by intelligent deathclaws as an entirely different matter!"

Deathclaws are by far, the scariest creatures in all of the fallout series. Used to be an old mod for fallout 3 and New Vegas that took these things into account. made deathclaws hunt for food and added hunting behaviors for them, ala mimicking voices and staying out of sight of the player, always stalking around to the sides behind cover. when deathclaws were hunting, it almost made the game neigh unplayable. not because of bugs or lag or glitchy issues, but because you couldn't leave town! litearly you'd hear their mimicked cries off in the distance, sounding like raiders or merchants or a bramen's bell... you'd normally go over to those sounds to either shoot the raider to loot his gear or go over to the merchant and the bramen to trade.... But then you ran into deathclaws! Loved that mod but scary as hell if you ever played it with one of the darker skies and realistic lighting mods.