A Skinwalker is a semidivine being which can morph into the general shape of any animal. Instead of being an exact copy of a gorilla, for example, it will be gorilla shaped (longer arms than legs, tremendous strength, etc.) but still recognizably a demon. The term skinwalker is actually a more general term for naagloshii and those who were taught magic by them.
Naagloshii are shapeshifters; they are evil and like hurting people. They capable sorcerers that can use their own natural abilities. The more afraid you are, the more powerful they become. They have a horrific psychic stench and when seen with a wizard's sight can be devastating and debilitating.
Naagloshii get stronger by eating the the essence of practitioners—they eat magic and add their victim’s power to their own. Eating a wizard gives the naagloshii considerable power; therefore, a wizards power attracts naagloshii, especially if the wizard is wounded. However, the longer the naagloshii stay away from their home tribal lands, the more power they lose.
Only a true shaman of the blood can drive naagloshii away by performing an enemy ghost way. 
The Naagloshii was virtually its own ley line, its own well of power, having an anormous amount of metaphysical mass. It disrupted even the dark flow of energy rising up through the tower on Demonreach. However, as it approached the cottage and the tower, the stone glowed with fox fire, revealing symbols in an unknown language that seemed to repel the creature away from the structures.
True skinwalkers are millennia old. They are typically only found in the American Southwest on tribal lands, it costs them power to stay away too long. The Ute and the Navajo and other south-western tribes have the real stories about them.
The English word for semidivine doesn't really cover it. Most skinwalkers are just people—powerful, dangerous people. They're successors to the traditions and skills taught to avoricious mortals by the originals—the Naagloshii. Shagnasty is a real Naagloshii. Per some Navajo stories, the Naagloshii were originally messengers for the Holy People when they were first teaching humans the Blessing Way. They were supposed to leave the mortal world with the Holy People, a few didn't. Their selfishness corrupted the power the Holy People gave them. It can be assumed this happened pre-history, several millennia ago.
Morgan tells Harry of a previous encounter with a skinwalker in which Morgan led it onto a nuclear test range and stepped into the Nevernever, leaving the skinwalker to be destroyed by a nuclear weapon. 
in the seriesEdit
- Main article: Shagnasty
It's often veiled and invisible. Harry got a brief glimpse when its veil hit Harry's shield: It was immensley tall, lean, shaggy, vaguely humaniiod thing with matted yellow hair, overlong limbs and long, almost delicate claws. Its long arms hung bellow its knees. It has golden eyes.
In Turn Coat, Shagnasty was sent by someone to find Harry and take Morgan from him. He abducted Thomas Raith. Harry set him up to bring Thomas to Demonreach island as well as the Council, and the traitor and whoever the real killer was. 
First introduced in the television series of The Dresden Files in the first episode, "Birds of a Feather", it can kill its victims and using its ability, skin them. Then it can take the form of the person. In the TV series it was destroyed with a magical energy amplifying and exploding device nicknamed the Doom Box.
- ↑ 1.0 1.1 Turn Coat, ch. 29
- ↑ Turn Coat, ch. 27
- ↑ 3.0 3.1 Turn Coat, ch. 6
- ↑ Turn Coat, ch. 45
- ↑ 5.0 5.1 Turn Coat, ch. 25
- ↑ 6.0 6.1 Turn Coat, ch. 4
- ↑ 7.0 7.1 7.2 7.3 Turn Coat, ch. 7
- ↑ Turn Coat, ch. 44
- ↑ Turn Coat, ch. 5
- ↑ Turn Coat, ch. 25-26
- ↑ Turn Coat, ch. 44 and 45
- The Original Merlin
- The Paranormal Pastor: The Navajo Skinwalker
- Navajo Skinwalker Legend | The Wichery Way
- Skin-walker - Wikipedia, the free encyclopedia
- What Is a Skin-Walker? - Wisegeek
- Skinwalkers - What Are They?
- What are Skinwalkers? - - Helium
- Shape Shifters in Native American Myths | eHow.com
- Skinwalker True Stories