Forerunners (Halo)

Forerunners is the translated name for an ancient race which ceased to exist 3 billion years before the events of the main Halo video game series. They are known for their advanced technologies, technologies that allowed them to build mega-structures like Halo Array, The Ark and the Shield Worlds. All that is known about the Forerunners was learned from the various artifacts of their creation, found on the planets Reach, Earth, Sigma Octanus IV, Harvest, Arcadia, Sanghelios, Kholo, and Janjur Qom. They were the preceded by another extinct race known as Precursors. While they took responsibility of preserving every life form in galaxy, they were threatened by the parasitic Flood. Through the use of the Halo weapons, they were able to all but defeat the Flood, seemingly at the cost of their own existence and much of the life in the ancient Milky Way galaxy.

Origin
The Forerunners were a very advanced civilization which came into existence after overthrowing another race known to them as Precursors, who were believed to be responsible for their creation. Only one Precursor known as The Timeless One survived and was locked in a time bolt on Charum Hakkor. After becoming the dominant species in the galaxy, their empire spanned over three million fertilized and inhabited worlds. The fact that the Halos were scattered all over the galaxy hints that the Forerunner Empire covered most, if not all, of the galaxy.

The Forerunners originated from the planet Ghibalb in the Orion complex. Their civilization was based on Mantle, a belief that it was their responsibility to protect all life in the galaxy. They presumably monitored the evolution of all other species in the galaxy, intervening in their evolution when necessary to make sure that they followed paths of peace, free of conflict. One such interference was the devolution of the human race due to it being considered a violent species. The Forerunners themselves were a race without conflict and at a point in history where they had reached disarmament. This disarmament was the main factor weakening the Forerunners against the Flood attack.

Human-Forerunner War
The Forerunners battled against humanity's interstellar empire in response to a perceived invasion of new colony worlds. Afterwards, the actual reason for the war was determined to be the Flood. To find replacements for Flood infected planets, humanity had encroached upon Forerunner controlled parts of the galaxy. The Forerunners saw humanity as a threat to their principle of Mantle and after defeating them, the Forerunners devolved humanity and exiled it to its home world Erde-Tyrene (Earth).

After the war with humanity, the Forerunners realized that the Flood could return and so created an array of galaxy-sterilizing super weapons as the ultimate defense against such a threat. The Forerunners also created Shield Worlds and The Ark to save information regarding all the species in the galaxy so that if a situation were to arise and the array fired, the galaxy could be reseeded with the samples of DNA stored upon The Ark. Thus, the Library Project plan was implemented, resulting in the creation of twelve massive ring-shaped mega structures collectively known as Halo-Array and The Ark.

The Warrior-servant class which supported the plans for the Shield World were removed and went nearly extinct, leaving the Forerunners ill-prepared for the upcoming Flood-Forerunner war.

Flood-Forerunner War and Firing of Halo-Array
On moving further on their pages of history they came in contact with extragalactic parasite known as the Flood on the planet G 617 g (details of this first contact are unavailable) they immediately recognized them as a threat to entire galaxy and tried to contain them. Believing the Flood to be a mere parasite and non-sentient disease resulted in failure in their countermeasures as they tried methods suitable for a disease and not a warfare.

After being unable to contain the Flood outbreak galaxy went into a state of war. During 300 years of conflict Forerunners soon realized that their conventional naval tactics were ineffective against Floods and hence new weapons and tactics were developed to combat them. Sentinels were deployed as a means of maintaining the Flood through surgical localized tactics. However these tactics proved effective but only to slow and never stop the expansion of the Flood, the Forerunner leadership realized that only way to stop was to deprive it of any and all hosts, thus eliminating its potential to grow.

To stop this the Forerunners created the Halo Ark as a weapon for last resort. The Ark was designed to starve the Flood to death by killing all sentient life with enough biomass to sustain them (as told by 343 Guilty Spark in Halo: Combat Evolved). There was debate as to whether to use the Halo Array or not resulting in civil war. It was decided that using the Array was the only option of stopping the Flood. Hence they did not start the war until it was too late.

The Gravemind managed to convince a contender class AI 032 Mendicant Bias, to unite with the Flood and led an attack of Forerunners. At last, the Forerunners activated the Halo array, killing themselves and all sentient life of sufficient biomass in the Milky Way, with the exception of those species safely placed on the The Ark.

Before their disappearance from the galaxy, the Forerunners would name humanity their successors, identifying them with the title "Reclaimer".

Society
The Forerunner civilization was mainly divided into five categories.

Builders
The Builders were responsible for the construction of a majority of Forerunner architecture. As such, they were responsible for designing and creating most of the Forerunners' megastructures, including the Halo Array and Onyx.

Miners
The Miners were the second-highest rate in Forerunner society. They were responsible for obtaining the materials required for the work of the Builders.

Lifeworkers
The Lifeworkers were the third-highest rate in Forerunner society. They specialized in biology and medicine, especially with the experimentation of various forms of life. It was not uncommon for Lifeworkers to receive their own planets for experimentation.

Warrior-servant
The Warrior-Servants were the fourth-highest rate and primary military caste in Forerunner society. They were responsible for, among other things, piloting war sphinxes during the Human-Forerunner wars.

Engineers
The Engineers were the lowest rate in Forerunner society, and were tasked with constructing and maintaining structures and machinery, as well as astroengineering.

Technology
Forerunner technology was much advanced. They had achieved Tier 1 level of technological advancement. The only Tier 0 level civilization was Precursors. They were able to manufacture solidified surfaces out of light by using technology known as hard light. Were even able to use slipspace to teleport between locations almost instantaneously, and create numerous forms of advanced machinery. They developed ability to initiate pre-mature stellar collapses of stars and create planets in less than 10,000 years. Had even mastered the use of various energy fields, including buffer fields which they used to manipulate gravity. They made constraint fields used to restrain individuals, confinement fields used to block the movement of entire ships, and the containment and collection fields they used to harness entire stars for energy production. and camouflaging technologies, including dazzlers (can generated visual and auditory delusions) and bafflers (can created geometric distortions that could effectively hide a large area not only from plain sight, but also a starship's sensors).

The more known of Forerunner technological creations are Halo-Array, The Ark, Onyx shield world and Dyson Spheres.