Darksmith

"'In the desert, there is this mysterious man. Whoever or whatever he follows is not known, however he is one of the greatest forgers in the universe.' - The Guide once at least one vanilla boss is defeated"The Darksmith is a NPC that will spawn in the Underground Desert where the player cannot see and the following criteria is met: While these must not all be true for the Darksmith to be alive, if he dies and the Moon Lord has been defeated, he will not respawn. The Darksmith also does not go out during the day.
 * At least one vanilla boss is defeated in the world.
 * The Moon Lord has not been defeated in the world.
 * At least 2 in-game nights have passed in the world.

If he is alive, however, he provides multiple quests and weapons to the player.

Quotes
"I heard of you. I knew this would happen. I shall join your side, hero." - When first talked to

"I have been caught. Quick!" - during the time between the destruction of the last Celestial Pillar and the summon of the Moon Lord

"Cthulhu? That's a name you hear everyday, is it not?"

"The sun is too powerful for my eyes." - At day

"What a beautiful day, I long to go outside and get a fresh breath of air!" - At night

"[name of Dryad] is a good child." - When the dryad is present

"Your steel is different than mine."

"You are great at protecting people, hero, but the danger of journey these days is unbearable." - In War Mode

Shop items
Darksteel Blade (If the world is in Pre-Hardmode) 4

Darksteel Knives (If the world is in Pre-Hardmode) 5

Darksteel Crossbow (If the world is in Pre-Hardmode) 5

Phantomsteel Greatsword (If the world is in Hardmode) 8

Phantomsteel Miniblades (If the world is in Hardmode) 9

Cannon Of Chaos (If the world is in Hardmode) 10

Ultralluminum Greatblade (If the world is in War Mode) 12

Ultralluminum Javelins (If the world is in War Mode) 14

Seven-Shot (If the world is in War Mode) 16

Trivia
The Darksmith is slightly faster than normal NPCs.

The Darksmith can teleport at night.

From the quote, "I have been caught. Quick!" and the time it is at, it is possible that the Darksmith and the Moon Lord have a connection.

The Darksmith seems to confuse day with night.