Wraith

Wraiths are Hardmode ghost-like enemies who can travel through blocks. They can inflict the Slow debuff on the player. They have black bodies, which render them almost completely invisible in dark areas, but have two glowing red eyes which are visible from within the darkness. They spawn at the surface layer at night.

Although Wraiths appear to fly freely, they can only hover slightly above the ground. They need foreground blocks to "swim" through in order to fly any higher.

Tips

 * Any structure built at least 6 tiles above the surface will prevent a Wraith from levitating up and into it.
 * Wraiths can be spawned pre-Hardmode by using a Wraith Statue.

Trivia

 * According to the Collector's Edition trading card, those who are devoured by an Eater of Souls become a Wraith.

History
Spectre 幻灵