The game follows Otto as he flees from his village after vicious hunters ransack it searching for a mythical creature. As one might imagine, Otto happens to bump into this very same entity (the titular "Troll") and, together, they embark upon a journey to escape from the hunters and save Troll. The entire campaign can be played with a friend locally so as the friendship between Otto and Troll grows during the course of the game, so, too, may your own friendship grow with your co-op partner.

Players assume the roles of Otto, a young boy whose village has just been turned into a life-sized Gomorrah replica, and a magical troll still in his infancy and lacking many of his brethren's abilities.  In a bid for survival, the two must traverse a ravaged Northern European landscape and probably crack wise about each other's mommas.