They were not any birds or bats known elsewhere on earth or in dreamland, for they were larger than elephants and had heads like a horse's. Carter knew that they must be the shantak-birds of ill rumour, and wondered no more what evil guardians and nameless sentinels made men avoid the boreal rock desert.
—H. P. Lovecraft, The Dream-Quest of Unknown Kadath
A shantak is a huge, scaly, birdlike creature with batlike wings, slimy skin, and two strong talons that lives in the Cold Waste of Earth's Dreamlands. Shantaks are sometimes summoned to serve as steeds. They are hunted by the Elder GodNodens and greatly fear nightgaunts.
Lovecraft, Howard P.  (1985). "The Dream-Quest of Unknown Kadath". In S.T. Joshi (ed.). At the Mountains of Madness and Other Novels (7th corrected printing ed.). Sauk City, WI: Arkham House. ISBN0-87054-038-6.