Building houses for NPCs (Non-Player Character) can be a quick way to get a head start in the game and a convenient way to protect yourself. To get NPCs to live in the house you’ve built, you’ll have to complete a task in order for an NPC to move in. The requirements depend on the NPC. This can range from defeating a boss or collecting a strange plant. NPCs have more things to sell depending on the time of day/night, moon phases, timely events (like the Blood Moon) or the biome. Some NPCs can also drop exclusive items when they depart (death). NPCs lower the spawn rate of most creatures, which can completely prevent monster spawns.