This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Fetch (Irish)
A fetch is a supernatural double or an apparition of a living person. The sighting of a fetch is regarded as an omen, usually for impending death. The fetch is described as an exact, spectral double of a living human, whose appearance is regarded as ominous. A sighting of a fetch is generally taken as a portent of its exemplar's looming death, though John and Michael Banim report that if the double appears in the morning rather than the evening, it is instead a sign of a long life in store.
As such, it is similar to the Germanic doppelgänger and to some conceptions of the British wraith. Sometimes it can be seen only by the one it imitates, and sometimes it can be seen by everyone except the person it imitates! Often it is grey and shadowy when seen from the corner of the eye, and is described as being airy in substance or not all there. The Fetch can also appear after a person has just died, walking among their loved ones, although seeming to be distant or distracted.