> [...] but simply flood the cave. This is Clonk, you know? ;-)

hmmm, I didn`t think about that. But you see... to flood the cave they would have to build a base, construct foundry, chop wood, mine copper and then produce pipes/wires (and that would need a building too), and also a windmill/power plant. So maybe the boss enemies should be at least partially immune to water. Also the caves could be so large, that it wont be possible to flood the cave (another idea would be to make a little hole at bottom of the cave, so the water won`t stay there. Players would have to lure monster to one end of cave, and then send someone to construct a bridge over the pit). And also some more fresh ideas from me.:
-No idea for a name - Strong one, can dig up and down, then he travels these tunnels with his four legs, and uses two hands to kill any Clonks that get into his territory.
-Ghost - He fights just as other Clonks, however every ten seconds he gets non-material and phases trough walls and floors. Strikes in most unexpected moments