Skeleton Merchant

The Skeleton Merchant is an NPC that sells items; he is found in the Underground and Cavern layers. He spawns randomly, similar to a bound NPC. Enemies will not spawn near him. He will not move into a vacant house, and will despawn when off screen.

His stock changes at 4:30 AM everyday and he does not need to respawn for it to do so.

He will throw bones to fend off nearby non-skeletal enemies.

Unlike other NPCs, the Skeleton Merchant does not have a map icon. A Hunter Potion will highlight him, but the Lifeform Analyzer will not detect him.

Quotes

 * "You would not believe some of the things people throw at me... Wanna buy some of it?"
 * "I'd lend you a hand, but last time I did that, I didn't get it back for a month"
 * "You've got a real backbone coming way down here, how 'bout ya buy somethin?"
 * "Stay away from the spiders. They'll suck out your insides and leave you a hollow shell of a man. Trust me on this one."
 * "Excellent! Someone's finally come by to take some of these maggots off my hands."
 * "There's no illness or condition that can't be cured by some of my Slime Oil! Trust me, it works, just look at my lively figure!"
 * "The only things constant in this world are death and taxes, I've got both!"
 * "Got any spare bones for sale? I'm looking to replace my broken hip... again."

Trivia

 * The names "Jack Sellington" and "Skellington" are references to Jack Skellington from "The Nightmare Before Christmas"
 * No-Eyed Willy is a reference to One-Eyed Willy from "The Goonies"
 * The name "Mandible Calavera" is a reference to Manuel "Manny" Calavera from "Grim Fandango"
 * The names "Billy Marrows" and "Gloomy Mays" are a reference to the TV salesman Billy Mays.
 * The quote about Slime Oil is a reference to the "Miracle Tonic" peddlers of the 1800s, who were commonly called Snake Oil Salesmen.
 * The quote about people throwing things at him is a reference to Diablo 3, in which an NPC named Squirt the Peddler says "I don't believe what people throw away. Wanna buy some of it?"
 * The quote "Stay away from the spiders. They'll suck out your insides and leave you a hollow shell of a man. Trust me on this one." may be a reference to his cause of death.
 * The quote "The only things constant in this world are death and taxes, I've got both!" is a reference to Benjamin Franklin's famous quote, "In this world, nothing can be said to be certain, except death and taxes."

History
Marchand Squelette