Cave 34 atm. at level 30, you'll get castles which can house 15 people. Also between leve l30~35, you'll get a new perk that will rase the gold, gems and dark mana dropped. There are a couple of walls that you have to pass, but after that wall you'll get quite the boosts. Just play smart.. :)
@kerusi: It seems perks do save for you. What browser and flash version are you using? Since the perks I fill in, reset after switching to another tab in the game. Even after using the dark ritual. I have 165 dark mana lying around that I can't use.
 "Cave Heroes"){kind=icon}
 "Greedy Pirates"){kind=icon}