Often incorrectly thought of as a snake reaching over 100 metres in length that can kill with a look, from the Harry Potter
series of books.
The basilisk is actually a 5 centimetre half-cockerel half-snake. It is hatched from a cockerel's egg (not a hen's; a cockerel's) by a toad. It can turn anything living into stone by glancing at it.
Mythologically, it was killed by forcing it to look into a mirror.