A Red Cap or Redcap, also known as a powrie or dunter, is a type of malevolent murderous dwarf, goblin, elf or fairy found in Border Folklore. They are said to inhabit ruined castles found along the border between England and Scotland. Redcaps are said to murder travellers who stray into their homes and dye their hats with their victims' blood (from which they get their name). Redcaps must kill regularly, for if the blood staining their hats dries out, they die. Redcaps are very fast in spite of the heavy iron pikes they wield and the iron-shod boots they wear. Outrunning a redcap is supposedly impossible.
Robin Redcap and William de Soulis 
As the familiar of Lord William de Soulis, a certain Robin Redcap wrought much harm and ruin in the lands of his master's dwelling, Hermitage Castle. Ultimately, he was taken to the Nine Stane Rigg, a circle of stones hard by the castle, wrapped in lead, and boiled to death. In reality William De Soulis was imprisoned in Dumbarton castle and died there, following his confessed complicity in the conspiracy against Robert the Bruce in 1320.
See also 
- Bluecap (Northumbrian English)
- Brownie (English and Lowland Scottish)
- Cofgod (Archaic English)
- Far darrig (Irish)
- Kabouter (Dutch)
- Kobold (German)
- Leprechaun (Irish)
- Nain Rouge (French)
- Tomte (Scandinavian)
- K. M. Briggs, The Fairies in English Tradition and Literature, p 57 University of Chicago Press, London, 1967
- Briggs, Katherine M. (1976). A Dictionary of Fairies. Harmondsworth, Middlesex: Penguin. p. 339. ISBN 0-14-004753-0.
- Mack, James Logan (1926). The Border Line Oliver & Boyd. Edinburgh.P. 146.