Selenian

The Selenian is a humanoid enemy that is spawned by the Solar Pillar during the Lunar Events. It is a ground based enemy that has 2 flaming swords, but can curl up and fly at high speeds towards the player. When it does this, certain projectiles you have fired at it will be reflected, like the Vampire Knives' projectiles. This is very dangerous as some weapons like the Sniper Rifle and Meowmere can potentially deal over 300 damage to the player. It is suggested to use Rockets against this enemy if you intend to play a ranged character.

Among the things they reflect:

-Bullets -Arrows -Sword beams -Vampire Knives -Nebula Blaze -Frost Hydra's shots-Lunar Flare

Among the things they don't reflect:

-Rockets -Scourge of the Corruptor -Flairon's bubbles -Terrarian -Star Wrath's stars -Last Prism -Lunar Portal Staff

Trivia

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