Piskies is the Cornish word for (perhaps) the better-known pixies of folklore. You'll find piskies in the Cornwall and Dartmoor areas of England, where their roots are thought to come from Celtic origins.
Often said to look like tiny old men with wrinkled faces and red hair, and with clothes made of moss, grass and lichen, these teeny pranksters are not unlike Brownies, who are known for being both mischievous and helpful, depending on their mood. Many a story involves a traveller being led astray across the moors by a naughty piskie.
What exactly are they? Well, the stories vary. Some believed them souls of pagans who could not transcend to heaven, or remnants of pagan gods pushed aside by Christianity. Perhaps the most macabre origin story relates to piskies being the souls of babies who had not been Christened. No guesses who like to spread that tale about. It was a favourite of Clergymen, and they used it to explain many other fairies of lore.
The Diabolus Chronicles features piskies in book four, The Greensward, when Pitch and Sickle encounter two little scamps who are fond of throwing rocks. I gave them a more 'natural' appearance, and imagine them as tiny twig-men with dew drop eyes and flower petal hands. But they have attitude in spades, and do very well at riling up an impatient daemon.
(Source- mysteriousbritain.co.uk)