Ghouls, Serpentines and Martichorae
There are creatures that resemble the cultured races, but exist only to prey on them. Lacking life and culture of their own, they prey on the other races, fattened by their prosperity. Like cuckoos, they excel at hiding themselves in the midst of their victims - if found out, they must usually flee or be destroyed.
Ghouls are feral beings that subsist of human flesh. However, they are even more craven than they are gluttonous, and so they tend to skulk around graveyards defiling the dead, rather than hunting the living. Those who wander close to a ghoul feast are likely to become one of the courses, though.
Generally, ghouls tend to hide carefully from the living, who hunt them down for defiling the dead. However, in times of dissolution, during plague, for instance, the ghouls grow bold, and they may be heard drumming and dancing in the night.
Ghouls are known for their filthy and vile ways, and for their awful graveyard stench. They are thought to look like feral humans with clammy, leprous flesh.
Three kinds of beings, their features a mix of hominid and serpentine traits, are said to exist. Whether these are mortal creatures or immortal spirits, there is agreement that they certainly prey on humans, particularily on children.
Martichorae (singular: martichoras), whose names mean "man-eater" in ancient Haramic, are considered one of the world's most dangerous creatures. While they lack the size and terrible breath of adult dragons, they are most cunning, and their venom is terrible and deadly. Martichorae look like great scarlet lions with the tails of scorpions and the faces of men. Their colossal jaws are set with triple rows of interlocking fangs.
It is furthermore said that martichorae may walk on two like men, and that they can even assume the guise of humans. However their appearance may change, their savage appetite is constant. Martichorae are creatures of the empty wastes.
[...]somewhere in sands of the desert
A shape with lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while all about it
Reel shadows of the indignant desert birds.
The darkness drops again; but now I know
That twenty centuries of stony sleep
Were vexed to nightmare by a rocking cradle[...]
(W. B. Yeats, The Second Coming)