A Foot-Long Snake That Became a Monster

In its earliest description the basilisk is small. Pliny the Elder reports a serpent of Cyrenaica about twelve inches long, marked with a white spot on the head like a diadem, hence basiliskos, "little king", which moves with its forepart raised, scorches vegetation, splits rocks and kills by breath and gaze. Lucan made its venom legendary; medieval bestiaries, drawing on Pliny through Isidore of Seville and the Physiologus tradition, added that the weasel alone could kill it and that it could be destroyed by the sight of its own reflection.

Over the Middle Ages the basilisk fused with the cockatrice, the creature said to hatch from a cock's egg brooded by a serpent or toad, until the two names became interchangeable and the small scorching snake acquired a rooster's head and wings. The lethal glance is the enduring element, and it is a literary and folkloric growth upon a modest zoological report rather than a feature of the original.