"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.” - Percy Bysshe Shelley
Basilisk are written in many shapes and forms throughout legend. The Latin "basilískos", means little king, and as such the Basilisk is frequently referred to as the king of serpents. Descriptions vary, some saying it is a crested snake of no more than twelve fingers in length, others that it's gigantic, and some drawings depict it as a dragon rather than a serpent. Though Serpents and dragons were largely interchangeable from the time period whence this creature was believed real. All fables of the Basilisk say it's gaze has the power to kill or turn victims to stone, and it is said to be created by hatching a chickens egg from underneath a toad.
Basilisks are not to be confused with Cockatrice, which are all but the same creature except that the cockatrice is a beaked bipedal wyvern.
Yeah, that's a Cockatrice. The Cockatrice and Basilisk are basically reversed versions of each-other, same powers, same parentage, but entirely different. But the Basilisk is always a snake and the Cockatrice is always a dragonish rooster.