Originating from the Greek-Roman mythology in which it was born from Medusa's blood, the basilisk was taken again in Middle Age in which people said it was born from a 7-year-old rooster's (rooster not hen !) egg brooded by a snake or a toad. It's a snake crowned or with a crown-shaped spot on the head and sometimes a dart at the tip of its tail, but people tend to mistake it with the cockatrice which has the same origins, weaknesses and powers : indeed the basilisk kills its victim with a single look straight in the eyes, in some versions because they emit toxic gas. But it can be killed by a mirror, the crow of a rooster and the weasel which is the only being who does not fear its look. However one thing the cockatrice doesn't have but the basilisk does : it can poison the earth and the water.

Basilisks © Greek-Roman mythology and Medieval European legends
Drawing © me