They are evil : during a war, they usually put some pieces of fire around the castle until it is only possible to walk there by knowing the position of them and avoiding them. Otherwise, the whole place really is a deadly trap.

     Please be careful. The trolls will ask you a lot of money for their work. However praiseworthy it may be, they seldom solve problems. Nothing will simply kill you if you're reticent to conversion. If you want to survive, you have to burn the rope before the entities score two eruptions.