The Lord of the Rings: Shadow of the East
Also called “Nackers” when spoken of in fairy tales by the folk of the Shire, and Raishburzum in Black Speech, they are one of the lesser abominations bred by Morgoth in the beginning of the world. He originally created them to hunt the ancient Elves of Beleriand and the Nan Anduin. The return of the Noldor to Middle-earth and the first rising of the Sun spoiled this plan. The Nackers could not abide the light of day and grew to fear all the Firstborn. They retreated to dark holes and places far beneath the earth. Only the disappearance of the Elves from Siragalë has given them the courage to return and test the beings of the surface world.
Nackers are Faerie, their place in Arda lost amid the evil manipulation of their breeding. They speak a debased formal Quenya, occasionally mixed with Black Speech, and bear knives and harness strangely reminiscent of ancient Nando styles.
Apart from their lineage, the Nackers of Undermarsh are a grotesque mockery of mortal life. Some three feet tall, they have the general build of goblins and the skin of lizards and serpents. Their faces are broken by fringes of skin, and wattles of hide and hair fringe their earless skulls. They boast sharp claws on their hands and feet, but use stone knives and axes freely. Their pointed teeth and yellowish slit eyes are those of a hunting animal. Their rough hide jerkins and the stonework of their altars are their only crafts.
While Nackers cannot breathe underwater, they can hold their breath far longer than a Man (6-10 minutes) and swim through water or mud as freely as a frog or turtle. They feed on fresh meat when they can get it, and on fish, frogs, grubs, and slime when they cannot. To breed, they need the blood and organs of mortals; these, sacrificed on their altars to the Pain-maker, “Dhaubâjor” or Morgoth, allow Nacker females to generate and fertilize their eggs.
Nackers are tough and resourceful; those troubling the Shire in the 17th century of the Third Age are ignorant of current events, but willing to push their luck as far it takes them. They have important physical gifts that make them deadly opponents. They are quite rational in combat, preferring to fight from ambush and take their prey with a minimum of risk. Blood lust occasionally overcomes them; they can be baited or lured into ambushes themselves. As suggested above, the Nackers believe all the Elves have left Siragalë and that the mortals supplanting their ancient enemies can be easily terrorized and eventually reduced to subservience.