Demolitionist

The Demolitionist is an NPC vendor that will spawn once the following criteria have been met:
 * There is an empty house.
 * You find either a stick of Dynamite or a Bomb.

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

The Demolitionist's appearance seems to be based on dwarves from many games, films and works of literature: he's significantly shorter than other NPCs and wears a beard. Furthermore, his mining helmet, lantern, and the fact that he sells explosives fit the trope of dwarves preferring underground environments.

Or maybe he's just a construction worker.