Sentinel Major

Sentinel Majors are artificial flying constructs designed by the Forerunners and serve on the Halo Installations. It is safe to say that they're upgraded versions of just sentinels.

Introduction
They are similar to a regular Sentinel, but are gold in color, have stronger blue beams, are protected by a light energy shield, and fire more accurately. They were only observed on Installation 05, however in the games, there are some in most of the levels containing Flood.

Sentinels have been known to have been created long before Installation 04 was ever conceived. They operated automated facilities such as Gas Mines like the one found on Threshold for "untold centuries" before the facility was redesigned to research the Flood. Therefore it is possible that they were only outfitted for combat after the Flood was discovered.

Function
The Sentinels are the "police" of the Halo installations, and are controlled by the Monitor of the Installation. Their primary purpose is to contain small outbreaks of Flood, however they can only manage flood for a short time. Should an outbreak grow beyond the sentinels' ability to control, Enforcers and Sentinel Majors are activated by the Monitor of the Installation to assist the Sentinels. It is also possible that there must be a massive outbreak, like the one on Installation 05, to give reason enough to construct these stronger versions.

In combat, their shields are less powerful than that of an Elite, and the beam fired is blue instead of orange. It is also more powerful, but its battery drains faster as a result. You can pick up this beam and the normal beam as your primary and secondary weapons. One can tell the difference between the weapons simply by noting that the stronger of the two is gold in color, rather than steel.

Trivia

 * Sentinel Majors do not appear in Halo 3 or Halo: Combat Evolved, however the Automated Turret somewhat replaces the Forerunner drone in Halo 3.
 * A Sentinel Major's Sentinel Beam fires a lustrous blue beam instead of orange and is stronger.
 * When a Sentinel Major's Sentinel Beam is dropped it takes the color of an average Sentinel Beam. When picked up, however, the color is gold like a Sentinel Major and the beam is blue.
 * It is presently unknown why the Sentinel Majors don't appear in Halo 3, it would've been entailed a weighty and influential combatant against the Flood and also considering that Installation 00 is one of the most prominent and important of Installations.
 * A possible glitch in Halo 2 is to pick up two Sentinel Beams, one is a regular and another is a Major.

Related Links

 * Sentinel
 * Enforcer
 * Constructor
 * Sentinel Launcher
 * Sentinel Production Facility
 * Sentinel Beam