NPC problems

[Stolen]

So, I'm relatively new to this game and I've got a problem. I had a few npcs move into my houses, but the moment I decide to make a house near a dungeon as a spawn point, the arms dealer decides to teleport across the whole world and live there instead. He won't move back, even after I destroyed his house.
Also, I can't get a dryad to move in, even after I've beat a few bosses. What should I do?

[cipnrkorvo /''>]

His housing (one before he moved) may have been invalid. You can check whether it is valid by going into the housing menu, clicking the question mark and clicking inside his house. If it says "This housing is suitable", then it's valid. If it says "This housing is not valid" or "This housing is missing a wall" or anything else, look up how to satisfy them. Then, also in the housing menu, you can force an NPC to move in by clicking on their icon in the menu and then clicking the house you want. He won't teleport back until both him and the house are off-screen.

[Stolen]

Interesting. Is it possible for me to get any other npcs to move in? For example: The Unconscious Man, he had a party with the arms dealer, even though they're a world apart.

[ImperviousAI]

Just make sure you have suitable available rooms queued up. NPCs can't share one room, they have to have their own individual room, even in the same house. And just like the person said up above, you can check if a room is suitable via opening your Inventory and clicking on the House Icon. There you can move your NPCs to whatever room is unoccupied.