In European bestiaries and legends, a basilisk (/ˈbæsɪlɪsk/ or /ˈbæzɪlɪsk/) is a legendary reptile reputed to be a serpent king, who can cause death with a single glance. According to the Naturalis Historia of Pliny the Elder, the basilisk of Cyrene is a small snake, "being not more than twelve fingers in length", that is so venomous, it leaves a wide trail of deadly venom in its wake, and its gaze is likewise lethal. Its weakness is the odor of the weasel and the tears of a griffin, which, according to Pliny, was thrown into the basilisk's hole, recognizable because some of the surrounding shrubs and grass had been scorched by its presence. It is possible that the legend of the basilisk and its association with the weasel in Europe was inspired by accounts of certain species of Asiatic snakes (such as the king cobra) and their natural predator, the mongoose.
The basilisk is called "king" because it is reputed to have on its head a mitre, or crown-shaped crest. Stories of the basilisk show that it is not completely distinguished from the cockatrice. The basilisk is alleged to be hatched by a cockerel from the egg of a serpent or toad (the reverse of the cockatrice, which was hatched from a cockerel's "egg" incubated by a serpent or toad). In Medieval Europe, the description of the creature began taking on features from cockerels. It has a venomous strike and in some versions of the myth has the ability to breathe fire.
There is the same power also in the serpent called the basilisk. It is produced in the province of Cyrene, being not more than twelve fingers in length. It has a white spot on the head, strongly resembling a sort of a diadem. When it hisses, all the other serpents fly from it: and it does not advance its body, like the others, by a succession of folds, but moves along upright and erect upon the middle. It destroys all shrubs, not only by its contact, but those even that it has breathed upon; it burns up all the grass, too, and breaks the stones, so tremendous is its noxious influence. It was formerly a general belief that if a man on horseback killed one of these animals with a spear, the poison would run up the weapon and kill, not only the rider, but the horse, as well. To this dreadful monster the effluvium of the weasel is fatal, a thing that has been tried with success, for kings have often desired to see its body when killed; so true is it that it has pleased Nature that there should be nothing without its antidote. The animal is thrown into the hole of the basilisk, which is easily known from the soil around it being infected. The weasel destroys the basilisk by its odour, but dies itself in this struggle of nature against its own self.