Tariaksuq
Region of origin: Arctic areas of North America
“Shadow people” of Inuit mythology, the tariaksuq are a race of beings, similar in nature to Iceland’s huldufolk, who lead comparable lives to the human societies they coexist alongside, but on a different plane of perception. They can never be directly observed and become invisible or formless when looked upon by a person, they or their shadows only ever caught as glimpses in the corner of one’s eye. They share this quality of obfuscation with the ijiraq, a malevolent spirit who hunts humans in the arctic forests, and the two have come to be thought of interchangeably, although the tariaksuq have been described as a half-human, half-caribou while the ijiraq is a shape-shifter taking on various animal forms at will. A tariaksuq may be rendered visible to humans after it has been killed.
The Compendium of Arcane Beasts and Critters 