This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Fext (Slavic)
A Fext is a mythical undead creature in Slavic mythology. Its origins are found in the terrors of the Thirty Years' War (17th century) in central Europe. It is said that the Fext is invincible to bullets, except bullets made of glass. Some of the great generals of that time were called Fexts because of their assumed immortality.
"Fext is a man vulnerable only by a bullet made of glass or a small stake used to tie young trees. Fext does not disintegrate after death and sometimes his corpse also shows a little activity like moving a hand if someone disturbs it. If a child is born in an amniotic cavity and this part of the placenta is carefully removed, dried, stored and later carried by the child under his left shoulder, the child will probably become a fext.