Welcome to the community

Pandora found, has alien ruins (PANDORA, GET IT? DONT OPEN THAT!)
Corps go there to look for resources
oh dang, no resources lets get out of here
planet devolves into bandits and anarchy
Dahl stays back because, hey everyone else left, no competition. maybe we can find some cool alien stuff
Dahl hires Tannis to poke around ruins
Tannis discovers vault, journal entry 345: I set the toaster to THREE, medium brown.
Atlas(One of the largest corps) finds out and pressures Dahl to get out
Dahl leaves and Atlas takes over (Tannis gets fired, screw you Atlas I'm giving my key pieces to crazy people by smuggling them out in my underwear)
ENTER THE HEROES
DONT TELL ANYONE ABOUT ME BUT IM GOING TO HELP YOU OPEN THE VAULT. ALSO I SEEM TO BE NAKED.
Oh look, everyone is Lilith
23 seconds later
END BOSS
I'm sorry I couldn't tell you about what was in there but if I had you might have ditched.
yeah yeah shut up crazy psychic lady you didn't actually do anything except say DO YOUR BEST! You didn't tell us any new info, you just made crap up on the spot.

zoom out to Hyperion satellite
DUN DUN DUNNNNNNNN

tl;dr
Stupid crazy psychic lady was just some woman at Hyperion(Atlas rival) using us to beat Atlas to the punch. No one actually knew what the Vault was. SURPRISE! Vault was Alcatraz, not Fort Knox.

make sense now?



Credit to: Genesis Genome over at the Borderlands Steam Forums