Selenian

The Selenian is a Hardmode, post-Golem enemy that is spawned by the Solar Pillar during the Lunar Events. It is a ground based enemy that has 2 flaming swords which curls up and flies at high speeds towards the player. When it does this, certain projectiles you have fired at it will be reflected. This is very dangerous as some weapons like the Sniper Rifle and Meowmere can potentially deal over 300 damage to the player.

Among the things they reflect: Among the things they don't reflect:
 * All bullets
 * All arrows
 * Some sword beams, such as those from Meowmere and Christmas Tree Sword, but not those from the Terra Blade or Influx Waver
 * Vampire Knives projectiles
 * Scourge of the Corruptor projectiles (main)
 * Nebula Blaze projectiles
 * Frost Hydra projectiles
 * Lunar Flare projectiles
 * All rockets (except Stynger, Jack 'O Lantern Launcher and Electrosphere Launcher)
 * Flairon's projectiles
 * Terrarian's projectiles
 * Star Wrath's projectiles
 * Last Prism's beam
 * Lunar Portal Staff's beam

Trivia

 * The word selenian means "lunar" and refers to Selene, the Roman goddess of the moon and sister of the sun-god Helios.