Medusa

Medusa is a Hardmode enemy found near Marble Caves. While being a relatively fast-moving melee attacker, Medusa also has the ability to inflict the Stoned debuff through her gaze. This debuff turns the player to stone: The debuff's onset is marked by Medusa's snake hair (as well as Medusa herself) lashing out red tongues, as well as a unique noise and particle effect, giving players notice before they are petrified. Players can avoid getting stoned by facing the other direction when the animation completes, or by having the Medusa's line of sight blocked by solid blocks.
 * The player will be unable to move or use weapons for the duration of the debuff, similar to being frozen.
 * Fall damage-negating accessories are disabled, fall damage is increased, and the minimum distance for fall damage is reduced.

The lower HP Medusa has, the faster she will move, similar to the Wall of Flesh.

Tips

 * Getting the Stoned debuff is very dangerous: If the initial fall doesn't kill the player, the few seconds of stun time could be long enough for Hoplites, Cave Bats, Giant Bats and other Cavern enemies to finish the job.
 * Be wary of large, vertical areas in the caverns (such as the Underground Jungle and player-made hellevators), especially when there's a marble cave nearby. The potential fall damage by itself can easily mince an endgame player.
 * Note that attacking the Medusa with most weapons will cause the player to turn towards her. Try not to engage her until she is within range or use a very accurate ranged weapon, so that she will become stun-locked before she has a chance to attack.
 * Facing away from Medusa while fighting off other enemies is recommended.
 * Yoyos, the Magic Missile, and the Flying Knife make great weapons against Medusa as they can be used from behind, and around corners, out of her line of sight. White String will extend the reach of yoyos by 4 or 5 blocks.
 * Ironically, the Medusa Head is also a great weapon against Medusa, as the player can use its "stare" while looking the other way.
 * Using the Feather Fall Potion can still protect the player from taking fall damage, even when they are Stoned.

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 Medusa was able to cause humans who looked into her eyes to turn into stone. According to Greek mythology, Medusa was turned into a gorgon by the goddess Athena.
 * The word "marble" is of Greek origin, as is "Medusa" and "hoplite" (which means "soldier/infantryman"). In Terraria, Medusa and Hoplites both spawn in Marble Caves.
 * The Banners of the Medusa and Hoplite do not show the image of the enemy on their corresponding Banners. The Medusa and Hoplite Banners displays a snake and skeleton respectively, with Greek-style patterns.

History
Médusa 메두사