Fire martens are ferocious creatures. Mostly they keep to themselves in the tops of trees, foraging for eggs and grubs and fruits, but they also hunger for stranger things, making unsuspecting travellers into targets.
Fire martens love coal, and any wooden thing that has been waxed. Crystals make for energetic moments of play until they are swiftly crunched and devoured. Old leather items are consumed without hesitation, and rust is licked and nibbled from metal surfaces.
Forests with fire martens are often very clean and quiet. Until a new traveller wanders in, and then the trees ring with the yowls and yips of excitable martens.