Interest? Nope, haven't heard of it.

In the map settings, you can specify that monsters can appear in a certain region. The system doesn't care about percentages and chances. Specify there 100 different monsters with a 1% chance of appearing and just wait. They'll all show up, one by one, and then they'll bunch up and beat the crap out of you. It's not supposed to work like that. Just because you meet an unfortunate goblin doesn't mean that while you're trying to sneak up on him, a nutiloid, a golden dragon, a couple of beholder and a pack of almirage should show up.