The basilisk is certainly more than just a large snake. Also known as a cockatrice, it has existed in legend for centuries. Rowling is just having fun in Beasts when she credits a Greek wizard named Herpo the Foul with breeding the first basilisk. Herpein is a Greek word meaning “to creep” that came to be a word describing snakes. The study of reptiles such as snakes is now called herpetology.

However, just as she suggests, by legend the basilisk was said to be the offspring of a rooster or hen mated with a snake or toad. Some artists followed that description literally, and drew strange beasts combining features from those animals. But more often the basilisk was portrayed as a serpent with a crown or a white spot on his head. Cobras, which have such marks, may be the origin of the basilisk legend.

The basilisk was reported to be deadly even from afar. The Roman naturalist Pliny said, “He kills all trees and shrubs, not only those he touches but all he breathes upon. He burns the grass, and breaks stones, so venomous and deadly is he.”

Some sources describe three varieties: The golden basilisk could poison with a look; another sparked fire; a third, like the famous snaky hair of Medusa in Greek mythology, caused such horror that victims were petrified.

William Shakespeare even mentioned a basilisk in his play Richard III. The evil title character kills his brother then immediately flatters his brother’s widow by mentioning her beautiful eyes. But she replies, “Would they were a basilisk’s, to strike thee dead!”