Medusa

Medusa is a Pre-Hardmode enemy, found at cavern level. Ordinarily a relatively fast-moving melee attacker, Medusa have the ability to inflict the Stoned debuff through their gaze. The debuff's onset is marked by the Medusa's snake hair lashing out red tongues, giving players a split-second to turn away. Players facing the Medusa when the animation completes will be turned to stone, completely immobilizing them and increasing fall damage.

Trivia

 * Medusa is the name of the most well-known of the Gorgons of Greek mythology: a species of creatures who look like women, have living serpents for hair, and cause humans who look at them to turn into stone.