Originally posted by freeck:

That's a good idea, mate, but it is already implemented in the game. Every time I meet a troll near a cave, the cave is empty. And vise versa - when I find a cave with no troll anywhere near it, the troll is inside.

Verify it yourself, just pay attention to the troll's location and see if you can find a cave nearby - it will most definitely be empty.

Pretty sure they meant having an event where the troll visually comes out of the cave in front of you. Which would be pretty cool