Precursor

"We meet again, young one. I am the last of those that gave you breath and shape and form, millions of years ago. I am the last of those your kind rose up against and ruthlessly destroyed. I am the last Precursor. And our answer is at hand."

- The Primordial addressing the Ur-Didact upon their meeting.

The Precursors were a race of beings preceding and possibly mythologized by the Forerunners, who believed them to be theoretical "Transsentient" beings, having the ability to travel among galaxies and accelerate the evolution of intelligent life. The Precursors achieved a higher level technological advancement than the Forerunners, being Tier-0, or Transsentience on the Forerunners' Technological Achievement Tiers.

History
Not much is known about them, but information that can be found by text from the logs stored in the Terminals around the Ark indicates it is possible that the Forerunner 'Mantle' (Guardians of the Galaxy and all life) was handed down from "legends of the past", the Precursors. It has been presumed that the Precursors viewed the Forerunners as their own legacy, continuing their work after they departed, much in the same way Forerunner lifeworkers (including the greatest lifeworker: the Librarian, or the Lifeshaper) viewed Humanity before the activation of the Array.

The Primordial, a Gravemind that identified itself as the last Precursor, revealed that the Precursors had been ruthlessly killed in a war with the Forerunners millions of years before the events of Halo and that "their answer is at hand" - implying that a proto-Flood form (described as a fine dust, contained in hundreds of glass cylinders) was created as revenge or as a failsafe. The fact that the Gravemind considered itself a Precursor implies that it was created by the Precursors as a means of revenge against the Forerunners. If so, their plan succeeded.

However in Halo: Silentium the Flood is revealed to be another form of Precursor, made via the powder referenced to in Halo: Primordium, which was also revealed to be actual Precursor dust. They were annihilated by Ancient Forerunners, who wished to seize the Mantle of Responsibility from the Precursors, instead of letting them give it to Humanity. Some Precursors went into hiding while some changed into the dust found by the ancient humans (later of which created the Flood). As the Precursors favored humanity, when the Flood attacked the galaxy they did not attack them for long. The Flood/Precursors found humanity worthy of the Mantle and instead traveled to take revenge against the Forerunners.

The Organon was created by the Precursors and was practically a web of information of billions of years of Precursor knowledge, also known as the Domain by Forerunners, showing how technologically advanced these beings had become. This technology was destroyed when the Halo Array fired, as they disable neural activity and all Precursor technology uses this form of energy to function.

Technology
The basis for all Precursor technology is neural physics. The Precursors were the only known civilization to achieve Tier 0 of the Forerunner Technological Achievement Tiers and to exceed the Forerunner in technological advancement. They can theoretically accelerate the evolution of all intelligent life and travel across galaxies. They also created the system that Forerunners use for storing information known as the Domain.

According to Bornstellar Makes Eternal Lasting, the Precursors were capable of engineering "orbital bridges" between planets in the same system, known as unbending filaments.

These orbital bridges, or 'star roads' were used in the final stages of the Forerunner-Flood war. They seemingly caused local space-time to warp and mutate when using their version of slipspace travel.

According to the Primordial, there is a possibility that Precursors are responsible for creating the Flood. This was proven true in Halo: Silentium when it was revealed the fine powder found and used by Ancient Humanity is actually the desiccated remains of several Precursors.

Trivia

 * The term Precursor means "One that precedes and indicates the approach of another." The term supports that it surpassed the Forerunner.
 * The Latin root word "trans" means "across" or "beyond." "Sentience" is the ability to experience sensation, and is often used to imply sapience, the ability to think. A transsentient being may thus be considered beyond any recognized being and be on the level of godhood.
 * In Halo: The Fall of Reach, Dr. Halsey uses the term Precursor to describe the alien race that created the crystal found on Sigma Octanus IV.
 * There is a possibility that the Precursors may have looked like or been what we call sea scorpions or eurypterids, as described by the Didact in the book Halo: Cryptum.
 * The Precursors' concept of Neural Physics is very similar to the Biotics in the Mass Effect series and/or the Jedi's belief of The Force in the Star Wars universe or in Star Trek where the traveler states that matter, energy, and thought are one in the same. Overall is the belief of "Mind over Matter" through science.
 * There is a possibility (according to the prisoner) the Flood was created by the Precursors, and would explain plausible extragalactic origins from a possible long term Precursor fail-safe plan, and not from an intergalactic Flood colony. If this is true, then it means that none of the Flood colonies in the Halo series have ever progressed past the interplanetary stage of development.
 * A creature of similar description is found on the secret, easter egg level in Marathon: Infinity, called "Hat's off to Eight Ninteen". The story tells of a creature nine meters tall, with four arms, and a substance in a transparent cylinder, and an invading race from the stars. To read the original text, click here. (7x117=819)
 * On the Halo 4 Forge map Impact a stange crystal like material can be found lodged in the center of the test lab found on the map this could possibly be a crystal similar to the one found on Sigma Octanus IV which was created by the Precursors.

List of Appearances

 * Halo 3
 * Halo: Cryptum
 * Halo: Primordium
 * Halo: Silentium