Nigon is the second underground race.

Hmm... I highly doubt that a hydra has six brains, one in each head. After all, it's not like it's six Siamese twin snakes (what a stretch, haha!), it has one brain. Maybe its brain isn't even in its head, like the stegosaurus had, or rather, it had a "posterior" brain in the pelvic region, which controlled many reflexes... Anyway, if you're interested, you can read about it on Wikipedia here:
http://ru.wikipedia.org/wiki/%D0%A1%D1%82%D0%B5%D0%B3%D0%BE%D0%B7%D0%B0%D0%B2%D1%80
But I think my point is clear. And Ettins are more like Siamese twins or some kind of mutants, so they have two brains and two minds.