Non-playable character

There is more information available on this subject at Non-playable character on the English Wikipedia.

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Non-playable character (NPC), or Bots refers to any character in a gameplay scenario whose actions are not controlled by the player, but rather through an artificial intelligence. Several modes include NPCs including Firefight, Multiplayer and most prominently Campaign.

Overview

There are three types of NPCs: hostile, allied, and neutral. Hostile NPCs will attack the player on sight with whatever is available at their disposal, or deter the player in some way. Allied NPCs will actively fight the enemies of the player and generally help them. Neutral NPCs will not engage in any combat whatsoever.

NPCs on either side have the ability to enter vehicles on the map. This can give either side huge advantages. NPCs can enter the turrets and side seats of larger vehicles, and drive certain vehicles. Which vehicles and the NPC's skill with them, is dependent on which game is played.

NPCs have unlimited ammo for their weapons. However, they must reload once they are done their magazines. In Halo 2, Halo 3, Halo 3: ODST, Halo: Reach, and Halo 4 the player can switch weapons with allied NPCs, helping to resolve issues of low ammo or help optimize combat efficiency for your team of NPC. Conversely, you can obtain slightly more powerful weapons that may not be available on the ground.

Some may feature unique triggers and dialogue that differentiate them from "normal" allies because they are vital to the development of the game's storyline.

Every Halo game allows the player to be stealthy and eliminate enemies from behind without alerting other NPCs. This mechanic is extended to have special animations in Halo: Reach, Halo 4, and Halo 5: Guardians called assassinations.

Gameplay

First-person shooters

Main article: First-person shooter

In Halo: Combat Evolved, there are several types of NPCs. Some of whom are important story characters like Captain Jacob Keyes and 343 Guilty Spark. Keyes is only seen a few times, but if he is killed, the mission is failed and you must restart the level. 343 Guilty Spark is invincible and immune to any attacks on him during the game. Avery Johnson and Marcus Stacker are two others but they can be killed with no repercussions.

In Halo 2, all NPCs are invincible. They usually fight alongside the player and lead allies into battle. Most of the time they are also armed with stronger weapons and feature unique dialogue that is integral to the storyline.

In Halo 3, they share the same characteristics of Halo 2's NPCs, but when they take too much damage, they will fall to the ground, lifeless, and stay there until the battle is over. Soon after, they will stand back up and utilize the nearest available weapon, which usually tends to be their own.

In Halo 3: ODST, the same rules still apply from Halo 2, though certain NPCs are playable in some campaign levels (for example, Tayari Plaza is told from Gunnery Sergeant Edward Buck's point of view, but he is an NPC ally in NMPD HQ). The only NPC excluded from the "invulnerable" rule is Vergil.

In Halo: Reach NPCs function more akin to those in Halo 2; they are invincible however still react to incoming fire. Unlike in Halo 2, however, the player cannot swap weapons with allied those in NOBLE Team. Halo: Reach also features the Fireteam system, which is a unique way of recruiting friendly AIs.

In Halo 4, Thomas Lasky is the only unique NPC. He is completely invincible and doesn't flinch when shot. Halo 4 Spartan Ops also features Parg Vol as an enemy who can be fought.

In Halo 5: Guardians, both Blue Team and Fireteam Osiris are unique NPCs that are dubbed "Musketeers" by 343 Industries. The Musketeers can take damage and go into a "final stand" or "down-but-not-out" state from which they can be revived. Similarly, the Musketeers can revive players in the same state. Musketeers can also be ordered by the player to take vehicles, attack enemies, look at different objects in the environment, take weapons and move to different locations. In the gametype Warzone, players can fight a variety of different NPCs to earn points including "Legendary" enemies that are specific to the maps they are fought on.

Halo Infinite will feature NPCs on multiplayer maps in special multiplayer training sessions. These "Bots" come in four types: Recruit, Marine, ODST, and Spartan.

List of Halo NPCs

Halo: Combat Evolved

Faction	Relationship to Player
UNSC Marines	Allied
Elites	Hostile
Grunts	Hostile
Jackals	Hostile
Hunters	Hostile
Sentinels	Allied (Until Two Betrayals, then hostile)
Flood	Hostile

Character	Relationship to Player	Levels Encountered
Captain Jacob Keyes	Allied	The Pillar of Autumn The Truth and Reconciliation
343 Guilty Spark	Neutral	The Library The Maw
Staff Sergeant Avery J. Johnson	Allied	Halo The Truth and Reconciliation
Lat 'Ravamee	Hostile	The Truth and Reconciliation

Halo 2

Faction	Relationship to Player
UNSC Marines	Allied
UNSC ODSTs	Allied
Elites	Allied (To the Arbiter) Hostile (To John-117)
Grunts	Allied (To the Arbiter) Hostile (To John-117)
Jackals	Allied (To the Arbiter until Quarantine Zone) Hostile (To John-117 and the Arbiter after Quarantine Zone)
Hunters	Allied (To the Arbiter) Hostile (To John-117)
Drones	Allied (To the Arbiter until Quarantine Zone) Hostile (To John-117 and the Arbiter after Quarantine Zone)
Brutes	Allied (To the Arbiter until Quarantine Zone) Hostile (To John-117 and the Arbiter after Quarantine Zone)
Sentinels	Hostile
Enforcers	Hostile
Constructors	Neutral (Appear as enemies in cross-hairs, but do not attack)
Flood	Hostile

Character	Relationship to Player	Levels Encountered
Master Gunnery Sergeant	Allied	The Armory
Commander Miranda Keyes	Allied	Cairo Station
Sergeant Major Avery J. Johnson	Allied	Cairo Station
Spec Ops Commander Rtas 'Vadumee	Allied	Sacred Icon
343 Guilty Spark	Neutral	The Oracle
Brute Chieftain Tartarus	Hostile	The Great Journey
Heretic Commander Sesa 'Refumee	Hostile	The Arbiter The Oracle
Prophet of Regret	Hostile	Regret

Halo 3

Faction	Relationship to Player
UNSC Marines	Allied
Elites	Allied
Brutes	Hostile
Drones	Hostile
Grunts	Hostile
Jackals	Hostile
Hunters	Hostile
Sentinels	Allied (Until Halo, then hostile)
Constructorss	Neutral (Appear as enemies in cross-hairs, but do not attack)
Flood	Hostile (Allied for only The Covenant)
Voi factory workers	Allied

Character	Relationship to Player	Levels Encountered
The Arbiter	Allied	All levels except Tsavo Highway
343 Guilty Spark	Neutral (Until Halo, then hostile)	The Ark Halo
Sergeant Major Avery J. Johnson	Allied	Sierra 117 Crow's Nest Halo
Commander Miranda Keyes	Allied	Crow's Nest
Gunnery Sergeant Reynolds	Allied	Sierra 117 Tsavo Highway The Storm Floodgate

Halo 3: ODST

Character	Relationship to Player	Levels Encountered
Gunnery Sergeant Edward Buck	Allied	NMPD HQ Data Hive Coastal Highway
Taylor H. "Dutch" Miles	Allied	Kizingo Boulevard NMPD HQ Kikowani Station
Michael "Mickey" Crespo	Allied	ONI Alpha Site NMPD HQ Kikowani Station
Kojo "Romeo" Agu	Allied	Kikowani Station
Captain Veronica Dare	Allied	Data Hive Coastal Highway
Unnamed NMPD Officer	Allied (Upon discovering Dr. Endesha's body if the player has collected 29 audio logs, turns hostile)	Data Hive
Vergil	Allied	Coastal Highway

Halo: Reach

Faction	Relationship to Player
UNSC Army	Allied
UNSC Marines	Allied
UNSC ODSTs	Allied
Elites	Hostile (Allied only if an Elite in Firefight)
Grunts	Hostile (Allied only if an Elite in Firefight)
Jackals	Hostile (Allied only if an Elite in Firefight)
Brutes	Hostile (Allied only if an Elite in Firefight)
Drones	Hostile
Engineers	Hostile (Allied only if an Elite in Firefight)
Hunters	Hostile (Allied only if an Elite in Firefight)
Moa	Neutral
Civilian	Neutral
Gúta	Hostile

Character	Relationship to Player	Levels Encountered
Carter-A259	Allied	Winter Contingency ONI: Sword Base Long Night of Solace The Package
Catherine-B320	Allied	Winter Contingency ONI: Sword Base Tip of the Spear Long Night of Solace
Jun-A266	Allied	ONI: Sword Base Nightfall The Package
Emile-A239	Allied	Winter Contingency ONI: Sword Base The Package The Pillar of Autumn
Jorge-052	Allied	Winter Contingency ONI: Sword Base Tip of the Spear Long Night of Solace
Sergeant Major Duvall	Allied	Exodus
Ardo 'Moretumee	Hostile	Long Night of Solace

Halo 4

Faction	Relationship to Player
UNSC Marines	Allied
UNSC Spartans	Allied
Elites	Hostile
Grunts	Hostile
Jackals	Hostile
Hunters	Hostile
Promethean Crawler	Hostile
Promethean Watcher	Hostile
Promethean Knight	Hostile
Sentinels	Allied

Character	Relationship to Player	Levels Encountered
Thomas Lasky	Allied	Reclaimer
Parg Vol	Hostile	Spartan Ops Episode 3 - Chapter 5: Hunting Trip

Halo 5: Guardians

Faction	Relationship to Player
UNSC Marines	Warzone Only. Allied and Hostile
Elites	Hostile
Grunts	Hostile
Jackals	Hostile
Hunters	Hostile
Promethean Crawler	Hostile
Promethean Soldier	Hostile
Promethean Watcher	Hostile
Promethean Knight	Hostile

Musketeers

Character	Relationship to Player	Levels Encountered
Petty Officer Second Class Linda-058	Allied	Blue Team Reunion The Breaking
Petty Officer Second Class Kelly-087	Allied	Blue Team Reunion The Breaking
Lieutenant, Junior Grade Frederic-104	Allied	Blue Team Reunion The Breaking
Spartan Olympia Vale	Allied	Every level excluding Blue Team Reunion The Breaking
Spartan Holly Tanaka	Allied	Every level excluding Blue Team Reunion The Breaking
Spartan Edward Buck	Allied	Every level excluding Blue Team Reunion The Breaking

Production notes

During the development of Halo: Combat Evolved, the Keelbug was conceptualized as a method to remove NPC dead bodies in order to free up memory in the game.