The artist and illustrator Theodor Severin Kittelsen (1857-1914) is one of the main reasons why a lot of Norwegians, myself included, just can't bring ourselves to accept the computer-animated trolls in movies like The Lord of the Rings: The Fellowship of the Ring or Harry Potter and the Philosopher's Stone. Good or bad animation aside - trolls just don't look like that, and we should know - because we've seen them. In fact, we grew up with them - by way of Kittelsen's works.
There is hardly a creature of Norwegian fairytales and myths that hasn't been portrayed by the artist, who was discovered while working as an apprentice for a watchmaker in Arendal on the South coast of Norway. and got free lessons at the School of Art in Christiania. The trolls, as told in folk tales and rendered by Kittelsen, come in several categories - the sea troll, the forest troll, the water sprite (Draugen in Norwegian), the sea ghost... All of them huge, ugly, hairy and bearing clear signs of where they live - ie the forest troll is covered in moss and sports a tree on his nose, and the sea creatures seem to be part of the water itself (in a truly creepy way that I will not at all try to put into language, as I would be bound to fail).
Kittelsen's name is also practically inseparable from those of Asbjørnsen and Moe, the most renowned collectors of Norwegian folk tales - as he came to illustrate several of their collections of stories. But even darker creatures than those depicted in these collections have been portrayed, not to say created, by Kittelsen - and I should also mention that his first portrayals of trolls came out too rough for the collectors of tales, who were afraid they would scare the children away. Kittelsen's series of pictures rendering The Black Death are dark, gloomy and intense. One of these creatures is Pesta, who is inspired by norse mythology and is a sort of incarnation of the plague. The most famous picture of Pesta is one of her creeping up the stairs, little more than her eyes and gaping mouth visible - but for Kittelsen this is more than enough to send shivers down our spines...
Not only did Kittelsen illustrate the writings of others, he also wrote himself. This is how he describes Pesta:
She was small, lean, and bent, her face greenish-yellow with black spots. Her eyes were squinting, dark and restless and set deep in her skull. Now and again a strange, evil light shone in them, and they flickered round in every direction, so that it was impossible to fix her gaze. Her head bobbed up and down. Her mouth moved rapidly - sharp and bitter. She was worse than the plague itself, I thought to myself, hence her name.
Beautiful pictures of Norwegian nature, such as that of Lofoten in Northern Norway, are also a widely appreciated part of Kittelsen's work - but his main achievement, and the one that will probably live the longest, is that of coining the appearance of the Norwegian trolls in such a brilliant manner.
Main sources:
http://www.cs.uit.no/~espensk/kittelsen/index-2.0.html (illustrated biography)
http://www.munchforlaget.no/galleri/galleri_kittelsen.htm (an online gallery)
http://fuv.hivolda.no/prosjekt/fuvbrynh/thkit.htm (in Norwegian)