In Terraria, NPCs (Non-Player Characters) are crucial for your progression, offering services, items, and more. Each NPC has specific requirements that must be met for them to move into your world. Here’s how you can attract and maintain NPCs in your Terraria game:

Basic Requirements for All NPCs:

• Housing: Every NPC requires a suitable house. A valid house must have walls, a floor, a ceiling, a door, lighting (like a torch), a table, and a chair. The house needs to be at least 10 blocks wide by 6 blocks high on the inside.
• No Corruption or Crimson: NPCs won’t live in or near areas heavily corrupted by the Crimson or Corruption biomes. Ensure their houses are built in safer areas.

Specific NPCs and How to Get Them:

1. Guide
   • Availability: Starts in your world.
   • Function: Provides crafting help and item tips.
   • Note: The Guide is the first NPC and is available by default when you create a new world.
2. Merchant
   • Requirement: Have at least 50 silver coins in your inventory.
   • Function: Sells basic tools, supplies, and some early-game items.
3. Nurse
   • Requirement: A player must have increased their maximum health (e.g., by using a Life Crystal).
   • Function: Heals player health and removes debuffs for a price.
4. Demolitionist
   • Requirement: You must have an explosive (like bombs or dynamite) in your inventory.
   • Function: Sells explosive items and demolition accessories.
5. Dye Trader
   • Requirement: Obtain a dye item or material that can be used to make dye.
   • Function: Sells the Dye Vat and various dye-related items.
6. Arms Dealer
   • Requirement: Have bullets or a gun that shoots bullets in your inventory (guns found in chests or dropped by enemies count).
   • Function: Sells weapons and ammunition.
7. Dryad
   • Requirement: Defeat any one of the early-game bosses (e.g., Eye of Cthulhu, Eater of Worlds).
   • Function: Sells seeds, plants, and nature-related powders.
8. Painter
   • Requirement: Have at least 8 other NPCs in your world.
   • Function: Sells paint and painting tools.
9. Witch Doctor
   • Requirement: Defeat the Queen Bee (found in the Jungle biome).
   • Function: Sells blowguns, summoner equipment, and fountains.
10. Stylist
    • Requirement: Found and rescued from Spider Caves, where she appears tied up.
    • Function: Sells hair dyes and can change the player’s hairstyle.
11. Angler
    • Requirement: Found sleeping on the sand of an Ocean biome.
    • Function: Gives fishing quests and rewards.
12. Goblin Tinkerer
    • Requirement: Defeat a Goblin Army, and then find him randomly bound underground.
    • Function: Sells reforge services, unique items, and materials for combining accessories.
13. Mechanic
    • Requirement: Found bound in the Dungeon after Skeletron has been defeated.
    • Function: Sells wiring tools and mechanisms.
14. Wizard
    • Requirement: Found bound in the Cavern layer after defeating the Wall of Flesh.
    • Function: Sells magic-related items and materials.

Tips for Managing NPCs:

• Space Them Out: While NPCs can be housed closely together, spreading them out can minimize the impact of enemy attacks during events.
• Biome Preferences: Some NPCs, like the Witch Doctor, benefit from being in specific biomes as they sell additional items.
• Protection: Ensure NPC housing is protected against enemy invasions, especially during Blood Moons and other events.

By meeting these requirements and providing suitable living conditions, you can attract a diverse range of NPCs to your Terraria world, each adding valuable services and enhancing your gameplay experience.