A basilisk is a legendary monster that can kill with a glance. It is also said to leave a trail of deadly poison in its wake. The basilisk was a staple of European bestiaries of the ancient era and the Middle Ages, in which it is often referred to as the king of serpents. According to legend, the monster is born of a serpent's egg hatched by a hen.
Though the basilisk is always reptilian, its form differs according to the source. Descriptions of the basilisk fall into three main categories, but there is a great deal of variation within each. The basilisk may be described as a snake, a lizard, or a cockatrice, another legendary creature that is half serpent and half rooster.
In each form, the basilisk is expectedly monstrous. Though one of the earliest sources of the legend, Pliny's Natural History of 79 CE, describes the basilisk as a small, though intensely poisonous, snake, in later versions, the monster is almost always gargantuan. Some descriptions of the basilisk give it many legs, others only a serpent's tail. In many versions, the monster has a crown-shaped crest, which is explained as the reason for the basilisk's nickname, the "king of serpents."
The deadliness of the basilisk became quite exaggerated in some accounts. It was said to be able to kill with its breath, with the sound of its voice, by breathing fire, by poisoning the air around it, by touching a living thing, and even by touching something that a living thing was also touching. According to legend, the basilisk is vulnerable only to roosters and to the sight of itself in a mirror. In the Medieval era, the basilisk became associated with alchemy. It was said to be essential to certain methods of turning copper or silver into gold.
In addition to the deadly basilisk of legend, there is a real animal known as a basilisk. Lizards of the genus Basiliscus are named after the mythical monster because of their crown-like crests, though they are neither giant nor poisonous. Basilisks are native to Central America and the surrounding areas and have recently been introduced to Florida.