The Manticore first entered the written record in the 5th century BCE through the Greek historian and physician Ctesias of Cnidus, who served at the court of Artaxerxes II, the Persian king who ruled the vast Achaemenid Empire. Ctesias wrote a work called the Indica, a book about the wonders of India based on the reports of Persian-speaking travelers who had journeyed to the subcontinent. In that lost book, preserved only in fragments quoted by later writers, Ctesias described a beast that the Indians called the Martikhora and the Greeks called the Androphagos, the Man-Eater. He claimed to have seen one such creature brought to the Persian king as a living gift from India, a red-furred monster the size of a lion with a human face, blue-grey eyes, and ears like a man's.

The Manticore's appearance was a patchwork of terrors. Its body was that of a lion, covered in red fur the color of cinnabar, and it moved with the speed of a stag across the Indian plains. Its head was human, with three rows of razor-sharp teeth in both upper and lower jaws, each tooth longer than a hound's fang. But its most deadly feature was its tail, which ended in a scorpion sting more than a cubit long, with additional stingers spaced along its sides and one atop its head. When attacked from a distance, the creature would raise its tail like an archer drawing a bow and launch these stingers through the air with deadly accuracy. When pursued from behind, it would stretch its tail to full length and shoot backward, striking hunters before they could close the distance. The stingers were a foot long and thick as a bulrush, and their venom killed every creature they touched, except for the elephant.

The Manticore's appetite was its defining horror. Unlike ordinary predators that might take a goat or a pig, the Manticore preferred human flesh above all other prey. It did not hunt alone but would lie in wait for groups of two or three men, then attack with claws and stingers together, slaughtering them all before devouring every part of their bodies. It consumed bones, clothing, and possessions whole, leaving no trace that anyone had ever been there. Its voice was said to sound like a flute blended with a trumpet, a strange and beautiful music that drifted across the desert and warned those who knew its meaning to flee. The Indian hunters who dared to pursue the beast rode elephants for protection, since the Manticore's stingers could not kill the great beasts, and they used spears and arrows to bring it down from a safe distance.

Not everyone believed the Manticore was real. The Greek traveler Pausanias, writing in the 2nd century CE in his Description of Greece, argued that the creature was simply a tiger, and that the stories of three rows of teeth and arrow-shooting tail stingers were exaggerations born of fear. The philosopher Apollonius of Tyana, as recorded by Philostratus, asked the Indian sages directly about the beast during his travels, and they told him they had never heard of such a creature. Aristotle dismissed all hybrid monsters as biological impossibilities, noting that animals of such different kinds could never breed with one another. Yet these skeptics could not kill the legend. The Roman writer Pliny the Elder accepted the Manticore as fact in his Natural History, and for fifteen centuries his authority made the beast a real animal in the eyes of European scholars.

In the Middle Ages, the Manticore migrated from the pages of natural history into the stone carvings of churches and the pages of illuminated bestiaries. It appeared in the De Proprietatibus Rerum of Bartholomew Anglicus, who placed it in India alongside bears and other carnivores. It was carved into the twelfth-century church of St Mary and St David at Kilpeck in Herefordshire, its human face and lion body frozen in stone for parishioners to fear. By the Renaissance, it had become a fixture of heraldry, its image granting noble families a symbol of ferocity and exotic power. In the sixteenth century, the geographer Gerardus Mercator included it on his maps of the world, and the English naturalist Edward Topsell recorded its Persian name as proof of its ancient pedigree. The Manticore had traveled from the deserts of India to the courts of Persia, from the skepticism of Greek philosophers to the certainty of medieval monks, and finally into the heraldic shields of English nobility, a monster that refused to die.