I can't seem to find any information on the real-world inspiration of this creature (it's from the "Monsters of Africa" article that also gave us the chepekwe, dingonek, and ngojama).
After investing an undue amount of time in research (alright, I spent a few hours Googling
) I haven't had much luck finding any solid info on the
Tyerkow. It appears to be based on West African folklore, which includes several forms of Vampire-like spirit.
The
Asabosam is a man-eating nocturnal jungle spirit that can masquerade as a human, but has iron teeth and iron hooks for feet. It likes to lurk in trees, from which it grabs up victims with its feet, rips out their throat with its teeth to drink their blood and then feasts on their flesh. Once satisfied, it will scatter whatever parts remain around the jungle floor. They'll sometimes toy with their prey like a cat with a mouse.
That doesn't sound much like a Tyerkow, so it must be a different monster.
There are also a variety of "witches" which look like ordinary humans during the day (they're often old crones, but could look like anyone), but take off their skins and fly around at night, often in the form of a fireball or while emitting fire from, ah, various orifices.
There are lots of different versions of this creature, such as the Ashanti's
Obayifo, and similar entities appear in Caribbean folklore such as the
Ole-Higue or
Soucouyant.
My suspicion is that a Tyerkow is some version of the latter kind of spirit,
