Fairies are a supernatural race of beings encountered in Torchwood, a spin-off series based within the Doctor Who universe, unlike most monsters in Doctor Who they are not aliens and are actually believed to be the creatures of legend.
However unlike the relatively sweet-natured fairies that popular culture has depicted these Fairies seem to be much more like the spirits of folklore - vindictive, cruel and often ugly they sought out human children to become "Chosen Ones" and protected them without mercy until they reached the age at which they would be transformed into Fairies themselves.
Fairies often killed those that angered them or threatened the "Chosen Ones" via pouncing them and choking them using rose petals - they were not beings of flesh and blood and did not exist in the same plane of existence as other beings, being able to travel effortlessly through time.
Fairies could choose to be seen in two distinct forms, the more traditional form of small butterfly-winged humanoids or their human-sized forms that were monstrous: though according to the show they could only be seen "from the corner of one's eyes" (a reference to real-life folklore).
Fairies have near-unlimited control over the elements, could only be photographed if they willed it and had seemingly been in existence since the Dawn Of Time - although humans had grown to see them as harmless little creatures the Fairies were always dangerous and deadly to those that provoked their wrath: though they showed an amazing degree of intelligence in this regard (they would murder without mercy those that angered them but would leave those they deemed innocent alone - such as when they murdered an entire car full of soldiers but left Jack alive, albeit alone in a car full of corpses).
- Fairies are obviously based on the real-world creature of legend and are actually fairly similiar to the fairies found in folklore - who are much more aggressive and dangerous than the fairies of popular culture.
- The idea of the "Chosen Ones" may of been inspired by the legend of Changelings.