In European bestiaries and legends, a basilisk (English pronunciation: /ˈbæzɪlɪsk/, from the Greek βασιλίσκος basilískos, "little king;" Latin Regulus) is a legendary reptile reputed to be king of serpents and said to have the power to 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 that it leaves a wide trail of deadly venom in its wake, and its gaze is likewise lethal; its weakness is in the odor of the weasel, which, according to Pliny, was thrown into the basilisk's hole, recognizable because all 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 (see "Rationalized accounts" below).
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.
One of the earliest accounts of the basilisk comes from Pliny the Elder's Natural History, written in roughly 79 AD. He describes the catoblepas, a monstrous cow-like creature of which "all who behold its eyes, fall dead upon the spot," and then goes on to say, "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 crow of a rooster 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." A putto kills a basilisk, symbolic of Swedish occupiers and Protestant heresy, on the Mariensäule, Munich, erected in 1638Isidore of Seville defined the basilisk as the king of snakes, due to its killing glare and its poisonous breath. The Venerable Bede was the first to attest to the legend of the birth of a basilisk from an egg by an old cockerel, and then other authors added the condition of Sirius being ascendant. Alexander Neckam (died 1217) was the first to say that not the glare but the "air corruption" was the killing tool of the basilisk, a theory developed one century later by Pietro d'Abano.
Albertus Magnus in the De animalibus wrote about the killing gaze of the basilisk, but he denied other legends, such as the rooster hatching the egg. He gave as source of those legends Hermes Trismegistus, who is credited also as the creator of the story about the basilisk's ashes being able to convert silver into gold: the attribution is absolutely incorrect, but it shows how the legends of the basilisk were already linked to alchemy in 13th century.
Geoffrey Chaucer featured a basilicok (as he called it) in his Canterbury Tales. According to some legends, basilisks can be killed by hearing the crow of a rooster or gazing at itself through a mirror. The latter method of killing the beast is featured in the legend of the basilisk of Warsaw, killed by a man carrying a set of mirrors.
Stories gradually added to the basilisk's deadly capabilities, such as describing it as a larger beast, capable of breathing fire and killing with the sound of its voice. Some writers even claimed that it could kill not only by touch, but also by touching something that is touching the victim, like a sword held in their hand. Also, some stories claim its breath is highly toxic and will cause death, usually immediately. The basilisk is also the guardian creature and traditional symbol of the Swiss city Basel.
The basilisk was, however, believed to be vulnerable to cockerels; therefore travellers in the Middle Ages allegedly sometimes carried cockerels with them as protection.
Leonardo da Vinci included a basilisk in his Bestiary, saying it is so utterly cruel that when it cannot kill animals by its baleful gaze, it turns upon herbs and plants, and fixing its gaze on them withers them up. In his Notebooks, he describes the basilisk, in an account clearly dependent directly or indirectly on Pliny's:
- This is found in the province of Cyrenaica and is not more than 12 fingers long. It has on its head a white spot after the fashion of a diadem. It scares all serpents with its whistling. It resembles a snake, but does not move by wriggling but from the centre forwards to the right. It is said that one of these, being killed with a spear by one who was on horse-back, and its venom flowing on the spear, not only the man but the horse also died. It spoils the wheat and not only that which it touches, but where it breathes the grass dries and the stones are split.
Then Leonardo says the following on the weasel: "This beast finding the lair of the basilisk kills it with the smell of its urine, and this smell, indeed, often kills the weasel itself."
 Rationalized accounts
Coat of arms, the biscione of the House of Visconti, on the Archbishops' palace in Piazza Duomo, Milan. The arms bear the initials IO.[HANNES] of Archbishop Giovanni Visconti (1342-1354)Some have speculated a rationalized explanation for the basilisk, in particular that reports of cobras may have given birth to the stories of the monster. Cobras can maintain an upright posture, and, as with many snakes in overlapping territories, are often killed by mongooses. The King Cobra or Hamadryad has a crownlike symbol on its head. Several species of spitting cobras can incapacitate from a distance by spitting venom, most often into the prey's eyes, and may well have been confused by similar appearance with the Hamadryad. The Egyptian cobra lives in the desert and was used as a symbol of royalty.
 Literary references
The basilisk appears in the Bible in Isaiah 14:29 in the prophet's exhortation to the Philistines reading, "Do not rejoice, whole country of Philistia, because the rod that beat you has broken, since the serpent's stock can still produce a basilisk, and the offspring of that will be a flying dragon." The King James version of the Bible states "out of the serpent's root shall come forth a cockatrice, and his fruit shall be a fiery flying serpent."
In Psalm 91:13: "super aspidem et basiliscum calcabis conculcabis leonem et draconem" in the Latin Vulgate, literally "You will tread on the lion and the dragon,/the asp and the basilisk you will trample under foot," translated in the King James Version as: Thou shalt tread upon the lion and adder: the young lion and the dragon shalt thou trample under feet," the basilisk appears in the Latin Vulgate, though not most English translations, which gave rise to its inclusion in the subject in Early Medieval art of Christ treading on the beasts.
In William Shakespeare's Richard III, a widow, on hearing compliments on her eyes from her husband's brother and murderer, retorts that she wishes they were those of a basilisk, that she might kill him. In Act II, Scene 4 of Shakespeare's Cymbeline, a character says about a ring, "It is a basilisk unto mine eye, Kills me to look on't."
Similarly, Samuel Richardson wrote in his famous novel Clarissa; or the history of a young lady: “If my eyes would carry with them the execution which the eyes of the basilisk are said to do, I would make it my first business to see this creature.” Another famous reference to the basilisk is found in John Gay’s "The Beggar's Opera" (Act II, Air XXV):
- Man may escape from Rope and Gun;
Nay, some have out liv'd the Doctor's Pill;
Who takes a Woman must be undone,
That Basilisk is sure to kill”.
Jonathan Swift alluded to the basilisk in a poem:
- See how she rears her head,
And rolls about her dreadful eyes,
To drive all virtue out, or look it dead!
‘Twas sure this basilisk sent Temple thence …
Alexander Pope also wrote that “The smiling infant in his hand shall take/ The crested basilisk and speckled snake” (Messiah, lines 81–82). In the chapter XVI of The Zadig, Voltaire mentions a basilisk, “an Animal, that will not suffer itself to be touch'd by a Man”. Percy Bysshe Shelley in his "Ode to Naples" alludes to the basilisk:
- Be thou like the imperial basilisk,
Killing thy foe with unapparent wounds!
Gaze on oppression, till at that dread risk,
Aghast she pass from the earth’s disk.
Fear not, but gaze,- for freemen mightier grow,
And slaves more feeble, gazing on their foe.”.
Shelley also refers to the basilisk in his poem "Queen Mab:"
"'Those deserts of immeasurable sand,
Whose age-collected fervors scarce allowed
Where the shrill chirp of the green lizard's love
Broke on the sultry silentness alone,
Now teem with countless rills and shady woods,
Cornfields and pastures and white cottages;
And where the startled wilderness beheld
A savage conqueror stained in kindred blood,
A tigress sating with the flesh of lambs
The unnatural famine of her toothless cubs,
Whilst shouts and howlings through the desert rang, -
Sloping and smooth the daisy-spangled lawn,
Offering sweet incense to the sunrise, smiles
To see a babe before his mother's door,
Sharing his morning's meal
with the green and golden basilisk
That comes to lick his feet." --Part VIII
Charles Dickens uses the Basilisk to describe Mrs. Varden's eternally angry and hideous housemaid, Miggs, in Barnaby Rudge: "But to be quiet with such a basilisk before him was impossible. If he looked another way, it was worse to feel that she was rubbing her cheek, or twitching her ear, or winking her eye, or making all kinds of extraordinary shapes with her nose, than to see her do it."
 Modern reuse
For basilisks in the Dungeons & Dragons fantasy role-playing game, see Basilisk (Dungeons & Dragons).Basilisks have been reimagined and employed in modern fantasy fiction for books and role-playing games, with wide variations on the powers and weaknesses attributed to them. Most of these depictions describe a reptile of some sort, with the power to kill its victims with a direct stare and petrify through an indirect one.
 Reuse in science fiction and popular culture
- For basilisks in the works of British author David Langford, see David Langford#Basilisks.
"Basilisk" and "Medusa weapons" are mythological terms used by various authors, notably David Langford, in Different Kinds of Darkness and related short stories to describe a (fictional) class of image or sensation which causes death or harm to anyone who views it.
'Basilisk' and 'Medusa' are also the names of weapons in the Warhammer 40,000 universe, so named for their ability to bring death and pain from a long distance.
Langford's fictional basilisk images, or BLITs, are so deadly to the characters that all information about them, including the death toll when they first appear in the story, is classified; however, each of them is given a name or number, and a reasoning common to such stories is provided. From Langford's fictional "comp.basilisk" Newsgroup FAQ: "...the human mind as a formal, deterministic computational system -- a system that, as predicted by a variant of Gödel's Theorem in mathematics, can be crashed by thoughts which the mind is physically or logically incapable of thinking. The Logical Imaging Technique presents such a thought in purely visual form as a basilisk image which our optic nerves can't help but accept. The result is disastrous, like a software stealth-virus smuggled into the brain." A mock-up of the first Basilisk image to appear in Langford's stories, known as "The Parrot," was generated by an enterprising fan and posted on a popular image-hosting website as a prank in late September, 2007.
Basilisk is also the evil mentor in the book Villain.net: Council of Evil. He has many powers and can remain immortal by draining energy from humans.
Basilisk: The Kouga Ninja Scrolls (バジリスク 甲賀忍法帖, Bajirisuku Kōga Ninpōchō?, 2003) is a Japanese manga and anime series. The manga was authored by Masaki Segawa and published in Japan in 2003 and 2004, based on the novel The Kouga Ninja Scrolls by Futaro Yamada published in 1958. The title Basilisk would refer to the main characters Kouga Gennosuke's and Muroga Hyouma'd ability to reverse the homicidal intent of anyone who meets his stare directly effectively causing them to kill themselves and Oboro's power to neutralize the techniques of any ninja who meets her stare directly.
In God of War: Chains of Olympus,the invading Persian forces own a basilisk that Kratos must kill.
 Reuse in Harry Potter
Main article: Basilisk (Harry Potter)The basilisk appears in J. K. Rowling's popular Harry Potter books, most notably in Harry Potter and the Chamber of Secrets, where it is the monster inside the depths of the chamber. In the book, and in the film sharing the same name, the basilisk is described as a large serpent whose direct glare causes instantaneous death. However, when looked at through something, such as a mirror, puddle, ghost, or the like, it causes petrification that can only be healed by a potion made from mandrakes.  Also, its venom is one of the most poisonous substances in the wizarding world. The only thing that can cure basilisk venom is the tears of a phoenix. Basilisks are said to be the creatures that spiders fear most, and basilisks fear only the crow of a rooster which is fatal to them.
In Rowling's book Fantastic Beasts and Where to Find Them, it is said that a basilisk is a green serpent that can grow up to fifty feet in length. It states that basilisks are believed to live for up to 900 years, and are only controllable by parselmouths, people with the ability to speak snake tongue (known as parseltongue). The book says that the basilisk was first created by Herpo the Foul, a wizard who hatched a chicken egg beneath a toad.
 Reuse in science
Basiliscus lizardMain article: Basiliscus (genus)Mythological concepts are sometimes co-opted in biological science to name animals, such as with "vampires", "lemures", "sirens", "dragons", and "harpies". "Basilisk" in science refers to Basiliscus, a South American genus of lizard containing four species.