Twilight Walker

The Twilight Walker is an NPC vendor that randomly spawns in the Corruption or Crimson Underground. He will not move into a vacant house if one is available, similar to the Traveling Merchant, Skeleton Merchant and the Old Man. He will despawn when off screen unlike the others. Eyes of the Twilight Walker are glowing, so it's easier to find him in darkness.

Quotes

 * "Oh my gosh! Did you see those toothy guys cruising around here? Don't worry! In this cave they will not find us!"
 * "You know, I just love this... cave! Here is everything - rot, a lot of rot, and many more strange statues and ominous altars... Isn't this nice?"
 * "Have you seen these huge orbs in the lower levels of the cave? I heard inside there are various interesting things! For example... a musket (/undertaker) ... and another musket (/undertaker) ... Just forget."
 * "I don't remember when the last time was left on the surface. But apparently, things are even worse there than here."
 * "You have no idea how glad I am to have met someone alive in these depths! Finally have someone to talk about my collection of dried wafers."

Blood Moon

 * "Do you also think that monsters are especially aggressive in this night?"

Trivia

 * The Shovelry set is a reference to the indie game, Shovel Knight.
 * The Red Cup and Blue Mug references Cuphead and Mugman from the game Cuphead, respectively.