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This Guide has been updated to 1.4. If you need to view the old 1.3 version of this wiki page, click here

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What is an NPC

An NPC is a "non-player character", in Terraria these are enemies, critters, townspeople, and rarely projectiles disguised as NPCs that you can damage (imp fireball, dark caster's water sphere).

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This page is very incomplete; For other NPC related pages, visit the wiki search bar

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Spawn projectiles

If you want your hostile NPC to spawn projectiles, first of all make sure the projectile you spawn is hostile and not friendly, so that it won't damage other hostile NPCs and so that it will damage players and friendly critters. This code usually goes in the AI hook. It shows the most common scenario: shoot one projectile from the NPC directly towards the targeted player (usually the nearest):

NPC.TargetClosest();
if (NPC.HasValidTarget && Main.netMode != NetmodeID.MultiplayerClient)
{
    var source = NPC.GetSource_FromAI();
    Vector2 position = NPC.Center;
    Vector2 targetPosition = Main.player[NPC.target].Center;
    Vector2 direction = targetPosition - position;
    direction.Normalize();
    float speed = 10f;
    int type = ProjectileID.PinkLaser;
    int damage = NPC.damage; //If the projectile is hostile, the damage passed into NewProjectile will be applied doubled, and quadrupled if expert mode, so keep that in mind when balancing projectiles if you scale it off NPC.damage (which also increases for expert/master)
    Projectile.NewProjectile(source, position, direction * speed, type, damage, 0f, Main.myPlayer);
}

You can emit the NPC.TargetClosest(); code if you already have it in your AI. You want to couple this usually with a timer, and if you want to spawn it some other way, ExampleGun showcases a few variants you can transfer over (logically, don't copy its code into the NPC, it won't work). Visit the NewProjectile documentation for more info.

Frequently Asked Questions

The NPC never spawns or disappears if spawned in manually

This can happen if you accidently wrote NPC.life = value instead of NPC.lifeMax = value in SetDefaults.

The spawned projectile deals no damage/disappears immediately

Make sure the Owner parameter in Projectile.NewProjectile is set to Main.myPlayer. A common misconception is setting it to NPC.whoAmI, which is not what the game expects. The owner exists to determine for what side/client to execute various logic on, such as dealing damage or handling projectile disappearing.

The spawned projectile deals way too much damage

In expert mode, NPC.damage is scaled up by 2 (by default). Various NPCs also scale in damage again once reaching hardmode (important if you use NPC.damage to spawn the projectile with). In addition to all of that, hostile projectiles gain an automatic x2 damage, with another x2 added for expert mode. If you want to counteract that, halve the damage before spawning the projectile, and again in expert mode.