Troll

Trolls are a humanoid race, seeming to be divided in some sub-races according to the place. In Daventry, Trolls are mostly vicious humanoid, disorganized and are met as solitary creatures of human size. As usual, they can be found guarding bridges, forbidding passage except of the toll, but are afraid of goats.

In the EGA remake of KQ1, the troll would sometimes attempt to attack King Graham in the woods after the sorcerer froze him, stealing his goods(this may have been a glitch however as it occurs rarely, and it may be a sprite swap with the Dwarf that does the same thing).

A cave troll lived in the cave underneath the waterfall leading to the Death Bogs of Tamir.

Thragaadash was a mountain troll living in the sorrowing court.

On the other hand, Trolls of the Vulcanix Underground known as Trollkin, in the land of Eldritch, stand six to seven feet tall and while not being the brightest and most civilized race, are kind and fair, if somewhat crude. That tribe enjoy eating beetles (much unlike their human eating cousins) and taking mud baths. These are ruled by King Otar Fenris III. For a while Rosella herself and Edgar was converted into trolls.

Real world
Trolls are creatures of the Northern mythology that lived underground, more like those in KQ7. Trolls made their way into modern fairy tales and folklore. In those traditions, they are usually believed to forbid people from passing bridges. There is a fairy tale(Three Billy Goats Gruff) of such a Troll, who was hit by a goat who wanted to pass the bridge, like in KQ1.