In Scottish folklore, the Fachan (aka Fachen, Fachin, or Peg Leg Jack) is a cruel and malevolent faerie with a very unusual appearance. It wields a spiked club, and uses it to chase away (and kill, if it can) anything that comes near it. It hates all other life, and will destroy whole farms and orchards in a single day. It is active all year, but you can recognize its lair quite easily, due to there being no trees, animals or grass, just barren ground. It only has one arm and leg, so it compensates for being extremely strong in those limbs.
It possesses a tuft of black hair or feathers on the top of its head, and has a very wide mouth, but its most unusual quality is quite obvious: It only has one of every body part (only one leg, eye, and arm). It is covered in fur. The appearance of the Fachan is so dreadful and frightful, it has been known to give the viewer a heart attack.