You tell him,
Yeah, I guard the Vault, but I'm on break right now.
Aw, you'll miss Gerald. He just left here a half hour ago to bust into the place. Said he was going to kill anyone in his way.
You blink slowly.
Finally, you say,
You know, I don't even know what it is I'm guarding. Do you have any idea?
All they say is it's the greatest treasure ever won by a mortal, says your barmate.
You've got to admit to yourself, that whets your appetite.
Ask the barkeep for a sandwich and some water to wash it down.
Finish your beer and run back to the Vault to see this treasure.