Meh. We've seen all of this before in various disaster movies. So many parts of Troll are predictable and I don't mean the story in general1, but individual scenes where you can easily guess what will happen or will be said. It has been done so many times before.
Giving this 2.5 stars because it's Norwegian and each country gets one "Get Out of Jail Free"-card. Another bonus for making the movie a short 96 minutes until the closing credits kick in. Roland Emmerich, please take note when creating your next abomination.
1 which is predictable too