First created by Herpo the Foul in Ancient Greece, the basilisk is known to be a notorious creature, and also dubbed 'The King of Serpents'. Breeding them has been illegal since mediaeval times due to the threat they cause. Thankfully, they are not the easiest to breed. Basilisks are born from a rare event when a chicken egg hatches beneath a toad.

Spiders are deemed the mortal enemy of this creature, as they will flee from it. Even acromantulas, who are capable of speech and just as dangerous, will stay away and will not speak the creature's name.

The basilisk can grow up to 50 feet in length and has been known to survive to around 900 years of age. Despite the age, basilisks are not immortal, and wounds from certain weapons (such as a goblin-made sword), or even the cry of a rooster, can cause a basilisk to die. They are dark-green with yellow eyes, and males have a feathery plume around their necks in vibrant scarlet. They also have several rows of sharp teeth and horns on their head. A basilisk will eat anything from birds and rodents to humans - anything to survive.

A basilisk's direct gaze has the ability to kill anything, and an indirect gaze causes petrification. A basilisk's venom is so potent that it not only causes death to any who are pierced by it, but it can also break down dark magic objects that cannot be destroyed by any normal means of magic (such as a horcrux). The tears of a phoenix are known to combat this venom if a person is lucky enough to be treated in time by one. The basilisk is not one that can be tamed or controlled, with the exception of those who are Parselmouth.