Subterranean Gold Pirates!
(When I'm at work, I'm usually doing my best not to work.)
I for one am not sure they warrant the application of the word 'pirate'. They're thieves and trespasses, but I don't sense pirate vibes from their activities.
I am also not sure how they do it. Underground for that long? My skin crawls at the thought. How do they not die of rickets? How do they not utterly destroy their eyes?