This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Knocker (folklore) (Cornish and Welsh)
The Knocker, Knacker, or Tommyknocker (US) is a mythical, subterranean, gnome-like creature in Cornish and Devon folklore. The Welsh counterparts are coblynau. It is closely related to the Irish leprechaun, Kentish kloker and the English and Scottish brownie.
The Cornish described the creature as a little person 2 ft 0 in (0.61 m) tall, with a disproportionately large head, long arms, wrinkled skin, and white whiskers. It wears a tiny version of standard miner's garb and commits random mischief, such as stealing miners' unattended tools and food.