Legendary creatures

A legendary creature is an animal or part-human being described in non-historical stories that sometimes involve the supernatural. In the classical era, monstrous creatures such as the Cyclops and the Minotaur appear in heroic tales for the protagonist to destroy. Other creatures, such as the unicorn, were claimed in accounts of natural history by various scholars of antiquity. Some legendary creatures have their origin in traditional mythology and were believed to be real creatures, for example dragons, griffins, and unicorns. Others were based on real encounters, originating in garbled accounts of travelers' tales, such as the Vegetable Lamb of Tartary, which supposedly grew tethered to the earth.

A variety of mythical animals appear in the art and stories of the Classical era. For example in the Odyssey, monstrous creatures include the Cyclops, Scylla and Charybdis for the hero Odysseus to confront. In other tales there appear the Medusa to be defeated by Perseus, the (human/bull) Minotaur to be destroyed by Theseus, and the Hydra to be killed by Heracles, while Aeneas battles with the harpies. These monsters thus have the basic function of emphasising the greatness of the heroes involved.

...
Wikipedia