Forerunner Forces

The Forerunner is the translated Covenant word for the ancient race that constructed the Halos and mysteriously disappeared leaving much of their technology behind. The Forerunner's technology is scattered all throughout the galaxy and it is rumored that the Prophets evolved on a planet that was once a Forerunner colony, which explains why the Covenant have such advanced technology. The Covenant believe that the Forerunner left their technology behind to aid them in their "Great Journey" which is why the Covenant revere and almost worship the Forerunner. However it is the ring shaped constructs named Halos by the Covenant that truly exemplify the Forerunners true genius, and hold the Forerunners greatest threat. The Halos were Constructed to contain and study a race called the Flood. For many years the Forerunner had battled the Flood meanwhile searching for ways to destroy them. They built large research stations filled with captured Flood specimens such as Lockout and the gas mining facility on the Gas Giant Threshold (the Arbiter level in Halo 2 where you kill the Heretic leader) desperately searching for any way to stop the Flood, but to no avail. After exhausting every other available option the Forerunner Constructed 7 Halos to contain the vast majority of the Flood, large galactic scale weapons of mass destruction the Halos could destroy all suitable hosts for the Flood within 25,000 kilometers and will also set the other Halos off too. After activating the Halos the Forerunner were all but destroyed leaving the Flood to slowly starve and die off. The Forerunner however left their robotic counterparts behind to watch over their now abandoned facilities, contain the Flood inside, repair, and maintain them

Monitors: On each Halo there is a Monitor, an incredibly intelligent A. I. roughly the equivalent to the UNSC's "smart" A.I.'s such as Cortana. The monitors are the only things on a Forerunner facility that are truly independent in terms of thinking because the guardians of the Halos such as the Sentinels are somewhat under his control. The Monitor on Installation 04 was 343 Guilty Spark, when the Humans released the Flood on Halo he broke out the Sentinels and attempted to enlist the "Reclaimer" (Master Chief) into acquiring the index and bring it to Installation 04's control center thus activating Halos main weapon.

Sentinels: Controlled by 343 Guilty Spark, these are the main guardians of Forerunner installations. Sentinels are hovering drones that are armed with a powerful laser for fighting against Flood. The Sentinels can only operate for limited periods of time, when not fighting they contract into smaller forms protecting the sensors and weapons. Some Sentinels are equipped with an energy shield similar to the Master Chief's or an Elite's. While projectile weapons are effective against Sentinels energy weapons work best.

Sentinel Enforcer: Also known as Sentinel majors, Enforcers are stronger, larger, heavy-weapons Sentinels. Enforcers are equipped with a forward energy shield that is impervious against small arms fire. It also has missile launchers, a rapid fire pulse weapon, and 2 grabbing arms that can lift up a vehicle and destroy it. These huge automatons are usually seen around the Sentinel Wall ( The area on each Halo that acts as a barrier to keep the Flood contained, it is deliberately deprived of sunlight making it a barren snowy wasteland) Sentinel Enforcers are mainly used against vehicles but can also destroy infantry targets quite easily from medium to long range. Sentinel Enforcers main weakness is if a soldier can get close enough and stick a couple of Plasma Grenades to its unshielded rear/underside then it can be damaged, to counter this Enforcers are almost always accompanied by regular more maneuverable Sentinels.

Constructors: These tiny robots are used for maintenance purposes, keeping Forerunner installations up and running. Although they do have a small laser used for welding and cutting it is not effective in combat, therefore if a Constructor is attacked Sentinels will immediately come to its aid.