I'm Not Going To Be Able To Sleep Tonight

Wiki:

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 inhabit ruined castles found along the border between England and Scotland. Redcaps are said to murder travelers who stray into their homes and dye their hats with their victims' blood (from which they get their name). It is said, 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 the buck-toothed faeries is supposedly impossible; the only way to escape one is to quote a passage from the Bible. They lose a tooth on hearing it, which they leave behind.

The most infamous redcap of all was Robin Redcap. As the familiar of Lord William de Soulis, Robin wreaked much harm and ruin in the lands of his master's dwelling, Hermitage Castle. Men were murdered, women cruelly abused, and dark arts were practised. So much infamy and blasphemy was said to have been committed at Hermitage Castle that the great stone keep was thought to be sinking under a great weight of sin, as though the very ground wanted to hide it from the sight of God.

Yet Soulis, for all the evil he wrought, met a very horrible end: he was taken to the Nine Stane Rigg, a circle of stones hard by the castle, and there he was wrapped in lead and boiled to death in a great cauldron.

The boiling to death end of Lord Soulis by his infuriated vassals is only Scottish folklore. 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.