I've won a few times, but as far as I known it's just luck based.

not only is it random, the rewards don't seem to be any better than Mallarchy Pond, so it's a lousy deal to my mind.
I kind of think that if you sacrifice a virgin to a volcano, your chances increase. Sort of anecdotal at best, though. Plus I'm running out of virgins.
- Well. I'm not entirely sure that'll work for me, then, especially as I don't happen to have a nearby volcano. I think I'll stick with the more universally accessible method of picking a spot with my eyes shut if I do actually play it again, but good luck with that :v