Unlike the others, I did not do this drawing on the train, but in my daughters house. I shared a photograph of the drawing whilst there, but as promised I am sharing a good quality scan now I am home.
As you can see a lot more detail is visible in the scan. Many of the more subtle troll faces were hidden in the photograph, but the scan has brought the details to life. I tend to think of trolls as a kind of nature spirit. Mischievous perhaps, from a human point of view, but guardians of the wild places and of animals and plants.
So I don't think these trolls mean the swan any harm, but are rather its guardians, looking over it and protecting it.
Other automatic drawings from the same trip: