In these enlightened days of science and technology and that, most people associate trolls with spiteful and/or mischievous people who anonymously trouble online folk.
Hiding under a bridge of secret identity, they wait until they hear the trip trap, trip trap of one of their triggers approaching, and start to send out messages that have only one intention – to make themselves feel strong.
Every time they provoke a reaction, especially a hurt emotional one from somebody, they feel for a moment a spike of bright joy.
They imagine themselves for that second to be powerful and beautiful, but of course, anybody else will see them for what they are- great lumpen ugly trolls with eyes as big as saucers and a nose as long as a poker.
In Scandinavian folklore these existed long before the internet was dreamed of, living far from human habitation and sometimes appearing as grotesque monsters, sometimes as normal people with only pale dry skin and a reddish cast to their eyes to identify them by.
The humanoid trolls were by far the most dangerous, of course, lulling people into a false sense of security before eating them up, snap snap snap.
These were also able to shape-shift into domestic cats when it suited their purpose but, like all their kind, had the fatal weakness of an allergy to sunlight.
As bothered as you can be by trolls during the hours of darkness, when the sun comes up they will be exposed and frozen in place, completely helpless to your whim, whether you choose to destroy them with a few well-placed blows or leave them as they are as an example to other trolls.