“The basilisk kills people by looking at them. But no one’s died — because no one looked it straight in the eye. Colin saw it through his camera. The basilisk burned up all the film inside it, but Colin just got Petrified. Justin… Justin must’ve seen the basilisk through Nearly Headless Nick! Nick got the full blast of it, but he couldn’t die again… and Hermione and that Ravenclaw prefect were found with a mirror next to them. Hermione had just realized the monster was a basilisk.
-- Harry to Ron (CS16)
Not a spell so much as a magical effect, caused by seeing the reflected eyes of a basilisk.
References from the canon
- The Petrification effect resembles death, except that the victim is still alive, as if in suspended animation. It takes careful examination to discern whether a victim is in fact Petrified rather than dead. If a ghost is Petrified, it turns a dark smoky grey and can only be moved by the use of a fan. The antidote is made from mandrake roots (CS9).
- The basilisk's stare is actually deadly. Each person (or creature) attacked in Harry's Second Year was merely petrified instead of killed outright because they did not look directly into the eyes of the great serpent:
- Mrs. Norris saw a reflection in the water on the floor
- Colin Creevey saw it through his camera lens
- Justin Finch-Fletchly viewed it through the ghost Nearly Headless Nick who was also petrified (since he couldn't die twice)
- Hermione and Penelope Clearwater saw the creature through a mirror they were using to look around corners
Middle French pétrifier "to make or become stone" (16c.), from Latin petra "rock, crag"
The legend of the Basilisk causing petrification may have evolved from tales of large cobras in Africa and Egypt that can spit venom:
Some have speculated that reports of cobras may have given birth to the stories of the basilisk. 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 crown-like symbol on its head. Several species of spitting cobras can incapacitate from a distance by spitting venom, most often into the prey's eyes... Source: Cryptidz Wikia