Sentinels (Halo)

Sentinels are fictional machines in the video games of Halo: Combat Evolved & Halo 2.

Overview
Sentinels are the guardians of the Halo installations, and are controlled by the monitor of the Installation. Known monitors so far are 343 Guilty Spark and 2401 Pentinent Tangent. The Sentinels were originally created by the Forerunners, an ancient (and supposedly extinct) alien race. They are now produced by large, airborne Sentinel Factories. They were created in order to guard the Halo installations and its structures. They are also tasked to keep the Flood from escaping Halo and spreading. Known forms of the Sentinels are: Minor Sentinels, Major Sentinels, Enforcers, and Constructors. All these types of Sentinels have different appearances and duties. According to the level "The Arbiter" in Halo 2, The Covenant sees the Sentinels as "holy warriors of the sacred rings."

Minor Sentinels
Minor Sentinels are the basic form of sentinels in Halo. These sentinels are the main guardians of Halo, and appears to be hovering drones with silver-color armor plating and armed with a laser weapon known as a Sentinel Beam. According to 343 Guilty Spark in the first Halo game, these sentinel beams are used to control the Flood, though they can only manage them for short periods. When not engaged in combat, they contract into smaller forms, concealing their weaponry. Few of these sentinels are equipped with energy shields (as seen in the last level of the first Halo game "The Maw"), though all sentinels are easily destroyed by any plasma-related weapons. In Halo 1, the sentinel beams are unusable and can only be controlled by the Sentinels themselves. In Halo 2, when a sentinel is destroyed, the sentinel beams can be picked up by a footsoldier, particularly a Elite or Spartan. Heretic Elites can be seen weilding the sentinel beams. The sentinel beams also made their appearance in Halo 2 multiplayer and can be usually seen in the map, Backwash.

Major Sentinels
First appeared in Halo 2, major sentinels are more advanced version of the minor sentinels. They are the same basic design as the minor sentinels, with two notable exceptions. One is the gold-colored armor plating replacing the normal silver-colored armor plating. Whether this is simply a color difference or a different armor alloy altogether is unknown. The second difference is that the Sentinel Majors are armed with advanced Sentinel Beams that fire blue-colored lasers instead of the weaker orange-colored beams that normal Sentinels use. These sentinels are also usually equipped with energy shielding that can absorb more damage than a normal Sentinel. When destroyed, a player may pick up the blue sentinel beam. It does more damage than the original sentinel beam, although it overheats and depletes a lot faster. Also, unlike the original sentinel beam in Halo 2, the blue sentinel beam never appears in multiplayer.

Enforcers
First appeared in Halo 2, Enforcers are massive robotic automations that serve to contain major Flood outbreaks. They are protected by an energy shield, but it only seems to protect the "front" on the machine. It is armed with rapid firing pulse beams (somewhat similar to the Needler weapon without the homing), and mortar-like projectiles. Its mechanical grabbing arms can pick up an entire vehicle and crush it if the driver is careless, but their arms can be destroyed with careful aim.

Constructors
On the beginning level of "Sacred Icon" in Halo 2, the player may see small flying devices that comes and fires a small-green laser on a destroyed part of a building. Additionaly, they can be seen opening pistons and travel through the hole inside. Constructors, are very small machines that mainly just repair damage to any Forerunner structure they find. They cannot be engaged in battle and if under attacked, the sentinels will come to their aid as they have no weapon system of their own (although their "green-laser beam" can actually do damage if the player walk up to it).