Demolitionist

The Demolitionist is an NPC vendor that will spawn once the following criteria have been met:
 * There is an empty house.
 * You have an explosive in your inventory.
 * Merchant is alive.

If the Demolitionist is killed, he will only respawn if the above conditions are met again. This means you must place an explosive in your inventory. Having them stored in Chests will not fulfill this requirement.

Items sold
Once the Demolitionist has moved into a house, he will sell the following:

Names
The demolitionist may have any of the following names:

Some of these names are references to dwarf characters, such as Gimli from The Lord of the Rings or Beldin from The Belgariad. Fikod and Urist are generic dwarven names from Dwarf Fortress. Durim is a corruption of Durin, a dwarven king mentioned in J.R.R. Tolkien's books.

Morthal is a name of a Hold Capital in The Elder Scrolls V: Skyrim.

Trivia

 * The Demolitionist's appearance seems to be based on dwarves from many games, films and works of literature. He is significantly shorter than other NPCs and has a beard. Furthermore, his mining helmet, lantern, and the fact that he sells Explosives fits the trope of dwarves preferring underground environments.
 * One of the Demolitionist's potential names, Gimli, is possibly a reference to The Lord of the Ring's widely known dwarf character. This is also a reference to how the Demolitionist looks like a dwarf.
 * Another of the Demolitionist's names, Urist, is a common nickname given to generic dwarves by Dwarf Fortress players, e.g. Urist McFisherdwarf, Urist McAxedwarf, etc.

Quotes

 * "Dynamite, my own special cure-all for what ails ya."
 * "Explosives are da' bomb these days. Buy some now!"
 * "Why purify the world when you can just blow it up?" (Only if Dryad is present.)
 * "It's a good day to die!"
 * "I'm sure [Name of Nurse] will help you if you accidentally lose a limb to these." (Only if Nurse is present.)
 * "I wonder what happens if I... (BOOM!)... Oh, sorry, did you need that leg?"
 * "Even [Name of Arms Dealer] wants what I'm selling!" (Only if Arms Dealer is present)
 * "Would you rather have a bullet hole or a grenade hole? That's what I thought." (Only if Arms Dealer is present.)
 * "Check out my goods; they have explosive prices!" (that one was bugged before 1.1)

Only at night:
 * "NO SMOKING IN HERE!!"
 * "If you throw this one in the bathtub and close all the windows, it'll clear your sinuses and pop your ears!"
 * "Wanna play Fuse Chicken?"
 * "Hey, could you sign this Griefing Waiver?"

Only during Blood Moon:
 * "I've got something for them zombies alright!"
 * "Hey, have you seen a clown around?" (Indirectly references that Clowns throw explosives)
 * "There was a bomb sitting right here, and now I can't seem to find it..." (Possible reference to Clowns carrying bombs)