Shagnasty is an evil skinwalker who likes hurting people. It's a capable sorcerer as well as using its own natural abilities. The more afraid you are, the more powerful they get.It has a horrific psychic stench and seen with a wizard's Sight, it can be debilitating.
It can eat magic, then adds its victim's power to its own. A wizard would give him a lot of power and that power draws them, especially a wounded wizard. The longer he's away from home tribal lands, more power it costs him.  Only a true shaman of the blood could drive a Naagloshii away by performing an enemy ghost Way.
It's often veiled and invisible. Dresden got a brief glimpse when its veil hit Dresden's shield: It was immensely tall, lean, shaggy, vaguely humanoid thing with matted yellow hair, overlong limbs and long, almost delicate claws. Its long arms hung below its knees. Golden eyes.
It may assume also the forms of: python-shaped blur, badger or wolverine; giant spider, one of Lara's security guard, a great bear-like something Gorilla-shape, something feline under a veil; Fight with Listens-to-wind: shadowy serpents (dozens), wolf-like shape, simian (ape-like) creature, ferret, alligator, falcon with fur turfts, four-legged bat-winged-thing with eyes and mouths everywhere—defeated, it ran off.
In the seriesEdit
- Main article: Turn Coat
In Turn Coat, When Harry Dresden was driving home, his senses told him he was being followed. He opened his Sight and saw the skinwalker. Seeing the pure mass evil perched on the roof of a building with his Sight nearly disabled him. He would See it repeatedly with every thought of it. He left his car and walked to Billy's where he used a quiet room to desensitize himself from it. It plagued his thoughts for the remainder of the novel.
While at Billy's, the skinwalker killed Kirby and badly wounded Andi Macklin, two members of the Alphas who were guarding Dresden while he was incapacitated. When Billy and Georgia in wolf-form double-teamed him, he turned into a hawk and flew away. 
Donald Morgan thought the Naagloshii must have followed him when he took the train from Tuscon. A wounded Wizard is easy prey and he'd gain much power by consuming him. Morgan tells Dresden 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. 
While Dresden and Anastasia Luccio were talking to Lara Raith at the Raith estate, the Naagloshii attacked. It charged into Lara's office, Luccio zapped it. It hit Luccio and wounded Justine in the belly, exited through the window and then reached through the floor and pulled Dresden down several stories and choked him for a while. Lara, and her two sisters Elisa and Natalia Raith engaged him. He ended up killing and wounding many. The Skinwalker said he had Dresden's brother, Thomas Raith, and demanded that Dresden trade Morgan for him. 
Murphy questioned why Dresden got stuck with two tails and suggests that Shagnasty—as Dresden now calls him—crashed into the Raith estate as a distraction to allow Madeline Raith to make her getaway. Shagnasty was the perps ace in the hole until Morgan escaped and he played his hole card feeling pressured. 
Shagnasty tortured Dresden's brother, Thomas Raith. He brings Thomas to Demonreach where Dresden squares off with him. In Dresden's final punch he uses a cord of force mixed with soulfire that nearly strangles him, but Shagnasty gets free by drawing a circle. Before he's kills Dresden he gloated, then slashed Dresden's face, giving Dresden a mean new scar. He taunts Dresden about Thomas, hunger-mad being in the tent with Molly. Toot-Toot attacks the Naagloshii with a utility knife, scores twice and runs, the creature shoots a force at Toot knocking into some thorny bushes, where he lay still. 
At the end of Turn Coat, it was eventually driven off by Joseph Listens-to-Wind, who himself morphed into various animals perfectly suited to defeating whichever animal the skinwalker was imitating. The Naagloshii's current whereabouts are unknown. 
- ↑ Turn Coat, ch. 6
- ↑ 2.0 2.1 2.2 2.3 Turn Coat, ch. 45
- ↑ 3.0 3.1 3.2 Turn Coat, ch. 25
- ↑ 4.0 4.1 Turn Coat, ch. 4
- ↑ 5.0 5.1 5.2 Turn Coat, ch. 7
- ↑ Turn Coat, ch. 26
- ↑ 7.0 7.1 Turn Coat, ch. 44
- ↑ Turn Coat, ch. 29
- ↑ 9.0 9.1 Turn Coat, ch. 30
- ↑ Turn Coat, ch. 5
- ↑ Turn Coat, ch. 25-26
- ↑ Turn Coat, ch. 44 & 49