This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Fachen (Irish and Scottish)
In Scottish folklore the fachan (or fachin, fachen, Direach Ghlinn Eitidh or Dithreach (dwarf of Glen Etive)) is a monster or giant described by John Francis Campbell in Popular Tales of the West Highlands as having a single eye in the middle of its face, a single hand protruding from its chest instead of arms, and a single leg emerging from its central axis.
It has a single tuft of hair on the top of its head, regarding which Campbell says "it were easier to take a mountain from the root than to bend that tuft." Campbell draws attention to the possible influence of creatures from Arabic tradition such as the Nesnas or Shikk, described as "half of a human being" and hopping about on one leg with great agility.