Acheri is mountain ghost in form of young female child in belief of Kumaoni people of Kumaon region in Northern India. It was introduced for European readers by First commissioner of Kumaon region G.W. Traill in his Statistical Sketch of Kumaon first published in 1828:

Acheri, or fairy, the ghosts of young of female children; these reside on the tops of the mountains, but descend at dusk to hold their revels in more convenient spots. To fall in with the train, at the time. is fatal, as the Acheri punish such intrusions with death: they occasionally also molest those who may cross the sites of their abodes during the day, more particularly females, who may have any red particles of dress on their person at the time, the Acheri bearing a peculiar antipathy to that color. When female children are taken suddenly ill, it is immediately concluded that the Acheri have cast their spell or shadow (chaya) on the child, with the view of adding her ghost to their numbers. The optical illusions and shadows, seen in various mountainous countries, are also occasionally visible on some of the mountains in this province, which are accordingly celebrated as the peculiar resort of the Acheri, as the processions of elephants, horses, &c., which sometimes appear on the summits, are naturally ascribed to those ideal beings. A hill opposite to Srinagar, is celebrated in this respect; the train of shadows which. from time to time, appears to move along its ridge, continues visible for some minutes, and is, in consequence, viewed by numbers of inhabitants of the town. It therefore certain, that these shadows originate in physical causes, and are not created by the imagination of individuals. The theory, by which this illusion is explained in other places, is particularly applicable here, as the shadows in question, are invariably seen at the same hour, that is, when the sun is sinking below the horizon

Traill G.W. Statistical Sketch of Kumaon (1199: p.66)

For more than a century and a half Acheri remained character of folklore of India and since then wasn't many additions to that story of Traill. In novel Dead Storm by Richar Seib Acheri is demonic female creatures "in a sense dead but not dead" and subdued to more powerful male demons by the name of Baykak in Odjibwe folklore (1202: p. 199). It is possible that this novel became the source of confusion as different books since then describe Acheri legend in its original Indian form as part of folklore both Indian and of Ojibwe's. Some exploited this idea even more like Corker Johnston in his docu-fiction book "Acheri Demon Haunting" (1201). The "intriguing" fact that such different people had the similar legend according to Johnston was due to the fact that both had paleocontact with race he calls "Ancient Aliens" (1201).

The Mythology of Supernatural by Nathan Brown claims that Acheri legend is of Native American origin and has nothing to do with Hindu folklore bringing no authentic evidence to support this. Red color on clothing became protection from Acheri from being endangering color in Traill's report .

In episode All Hell Breaks Loose: Part One (2.21) of Supernatural series Acheri appeared as demon able to manifest itself in a form of a little girl without possessing human body