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|“||Once he stopped at a farmhouse well for a cup of water, and all the dogs barked affrightedly at the inconspicuous Zoogs that crept through the grass behind. At another house, where people were stirring, he asked questions about the gods, and whether they danced often upon Lerion; but the farmer and his wife would only make the Elder Sign and tell him the way to Nir and Ulthar.||”|
Lovecraft described the Elder Sign only once in his writings, as given by the aged alcoholic Zadok Allen in "The Shadow Over Innsmouth" (1936): "In some places they was little stones strewed abaout — like charms — with somethin' on 'em like what ye call a swastika nowadays. Prob'ly them was the Old Ones' signs." In this story, the sign is used as a defense against Deep Ones; apparently, the Deep Ones cannot harm someone protected by an Elder Sign. However, Lovecraft is known to have drawn it in at least one of his correspondences as a single line with five shorter lines branching off.
August Derleth, who wrote several Cthulhu Mythos stories, described it as a warped, five-pointed star with a flaming pillar (or eye) in the center. This latter description, which is featured in his novel The Lurker at the Threshold (1945), has become the most well-known and popular version of the Elder Sign. It is the version used in D&D, described in Deities and Demigods as an icon of green soapstone, and also appears in Chaosium's Call of Cthulhu role-playing game — as well as the later version published under the Open Gaming License — and in the video game Call of Cthulhu: Dark Corners of the Earth as well as in the boardgame Arkham Horror, produced by Fantasy Flight Games.
A third version of the Elder Sign, incorporating both Derleth's description and Lovecraft's drawing, appears in Lin Carter's short story "The Horror in the Gallery" (1976). This version places Lovecraft's branching design as a cartouche in the center of an oval "star stone". According to the fictional Book of Iod, one of the numerous arcane tomes mentioned in the Cthulhu Mythos, the Elder Sign is a powerful weapon against the servants of Cthulhu and the Outer Gods, and can be used to drive them off.
In other media 
The Elder Sign is mentioned in "Allan and the Sundered Veil", a short story found in The League of Extraordinary Gentlemen, Volume I. The short is highly inspired by the Cthulhu Mythos and describes an African woman using the sign to drive out an otherworldly being that has possessed Allan Quatermain. The sign described matches the star pattern but is a heptagram rather than a pentagram.
In the tabletop role-playing game Dungeons & Dragons, creatures from the Far Realm can sometimes be warded off by the so-called 'Cerulean Sign', which is depicted as a stylized white tree with five branches on a cerulean background. The depiction and use of this corresponds with those of the Elder Sign (or at least the version of the Elder Sign that has the shape of a branch or a pine tree), since the Far Realm is heavily Lovecraftian in nature.
In The Cabin in the Woods, a five-sided, swastika like design has been crafted into the floor of the ritual chamber. Beneath it the "Ancient Ones" lie slumbering.
- Derleth, August; H. P. Lovecraft (2003) . The Lurker at the Threshold. Pub Group West. ISBN 0-7867-1188-4.
- Harms, Daniel (1998). "Elder Sign". The Encyclopedia Cthulhiana (2nd ed. ed.). Oakland, CA: Chaosium. pp. 98–99. ISBN 1-56882-119-0.
- Petersen, Sandy. Call of Cthulhu (5th ed. ed.). Oakland, CA: Chaosium. ISBN 1-56882-148-4.