RPGs

Non-christian trolls

Trolls originate from Nordic folklore and mythology. They were part of those for a very long time, possibly from when the norse established themselves in Scandinavia.
Christians did not like them, depicting them as rock-throwing pagan monsters. The concept of trolls not being christians implies that there were christians around in substantial numbers, which in Scandinavia was not the case until about the 9th - 13th century CE.
Christian trolls differed from their older, 'pagan' predecessors. They are older in appearance, slow and strong but stupid. They are described as having big noses and sometimes multiple heads. Some were somewhat civilized, looking quite human and living in family groups, though they were unfriendly or even hostile to people. Others roamed free, hunting both animals and humans. Christian monks claimed that trolls were chased away not by lightning (see below) but by church bells and that they sometimes attacked churches under construction. Thus the writers shrewdly equaled human religious opponents with trolls.

Prose Edda

The Prose Edda is one of the few written accounts of what once was an oral tradition. It was written in the 13th century by christian literate skalds, not their well spoken pagan ancestors. As such, it yields a distorted view of earlier Nordic mythology. Still, it is a valuable resource.
In one poem in the Prose Edda a troll encounters the 9th century skald Bragi Boddason. In the encounter, she describes herself. The text, with a translation based on those of Anthony Faulkes and John Lindow, together with annotations:

Clearly this particular troll is not dim-witted. She is a follower of the seeress, defies lightning and is smart enough to steal from giants.

Modern fancies

• The idea of trolls residing under bridges comes from the 19th century fairy tale "The Three Billy Goats Gruff". The three goats are hungry and want to cross a bridge to reach green pastures, but under the bridge lurks an evil troll who eats anybody who tries to use it. At the end the largest goat defeats the troll in brief combat. This story has been copied an modified several times since its origin.
• The idea that trolls have tails also originates from the 19th century. Illustrator Theodor Kittelsen, who added pictures to Henrik Ibsen's poem "Peer Gynt", on an artistic whim drew his trolls with tails, which traditionally were associated with huldrefolk (see below).
• The near indestructible, wound regenerating troll that can only be destroyed by fire stems from Poul Anderson's novel "Three Hearts and Three Lions". Some games like Dungeons & Dragons have copied this kind of troll fantasy. There they are large and skinny.
• In Terry Pratchett's Discworld novels there are trolls who are composed of and eat rock. They steadily grow larger with age, from pebbles to mountains. Their intelligence is inversely proportional to the temperature of the environment. While original and funny, Pratchett's trolls are not the real thing.
• Trolls that practice voodoo and appear African or Afro-American are not Scandinavian at all. They were concocted by the people behind the wargame Warcraft.
• In modern games and movies there are trolls that look like supernatural body builders raised on steroids. These are the idea of people who like men with bodies stuffed with steroids. These muscle boy trolls are often confused with ogres, who like trolls have a rather different origin, being boogeymen rather than bone crushers.

Troll dolls

True trolls