Basilisk is a biblical term for a venomous serpent, though the name originally referred to a legendary “king serpent.” The exact species intended in the biblical passages cannot be determined; the term may refer generally to a dangerous snake.
The basilisk appears in passages describing poisonous serpents and their danger. Isaiah also pictures idols being cast to creatures of dark places, including the animals associated with the basilisk tradition.
The name comes from a word meaning “kinglet” and was connected in ancient lore with a crown-like mark, deadly breath, and a fatal gaze. The supplied material notes that the myth may have arisen from harmless snakes with crownlike markings.