1000px-ME3 Leviathan Creature

"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 Last Precursor

The Precursors (Latin: Maiores Invicta, meaning "Eternal Forefathers"), also known as Leviathans by humans, are an ancient aquatic race that dominated the galaxy in the time before the reign of the Forerunner, 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 Scale. Proud and aloof, they regard themselves as the galaxy's first and only apex race, and all other races are merely tools meant to serve them. With the advent of the Reapers, the Leviathans were forced into hiding to preserve themselves, and were content to observe the Reapers' harvests while surreptitiously erasing any evidence of their existence over the course of hundreds of millions of years.


The Leviathans are massive in size and possess a resemblance to Earth cuttlefish or squid. Two sets of three eyes are embedded symmetrically on the lower dorsal surface of the body. Several tentacle-like appendages extend below the body and from the sides. The Leviathans' exterior is covered in bony, heavily ridged plates. As Leviathans are aquatic, it is believed that they can breathe oxygenated water and their bodies can withstand both the extreme pressure of ocean depths and the lesser pressure of coastal areas.

The Leviathans possess the natural ability to influence the behaviors of lesser-minded organisms to the point of complete physical and mental control, an effect that is similar to indoctrination. They can use this ability to communicate with other beings in a manner similar to telepathy, as well as to turn them into thralls. The exact mechanics of this ability are unknown, but it has been compared to the rachni's theorized ability to communicate using an organic quantum entanglement communicator analogue that stimulates neural activity. Over-exertion of this mind-control ability causes nosebleeds in humans, and in extreme cases can lead to brain damage and death.

It is possible that the Leviathans further enhanced themselves cybernetically, allowing them to use element zero to travel through space and breathe air with the use of filtration systems. They might even have modified themselves with biotic amplifiers. In addition, their faster-than-light communication pulses require precise control with technology completely unknown to modern science.



The early history of the Precursors is completely unknown, but it is speculated by Task Force Aurora that they evolved on an unknown planet that also produced at least one other sapient species. The Precursors developed the ability to communicate with and dominate land-based sapient species to serve their purposes.

1000px-ME3 Leviathan wall illustration

A primitive illustration of a Precursor

Eventually, the Precursors utilized this thrall species' civilization to achieve spaceflight and spread throughout the galaxy, despite their immense size and aquatic nature. Every new species they encountered was enthralled to serve them and provide "tribute", and in return, the thralls were cared for and protected. With their dominance assured, Precursors considered themselves the galaxy's apex race. 

As Understood by the ForerunnersEdit

Little is known about the Precursors, other than that the Forerunners believed that the 'Mantle' (the role of guardianship of the galaxy and of all life) was bestowed upon them by the Precursors. From a Forerunner perspective, the passing of the mantle secured the Precursors' legacy in the form of the Forerunners, continuing their work after they departed, much in the same way Forerunners came to view humanity shortly before the activation of the Halo Array. The Forerunners believed the Precursors had shaped the Forerunner in their own image, and some even suggested that they may have done the same with humans. By the time of the Human-Forerunner war, prehistoric humans also claimed to be the sole inheritors of the Mantle, something the Forerunners considered heretical at the time.

The TruthEdit

"We are the Reapers. We gave them form. There is no difference. Until all space and time are rolled up and life is crushed in the folds... no end to grief, war or pain. In a hundred and one thousand centuries... unity again, and wisdom. Until then - sweetness."

In actuality, the Precursors were responsible for seeding the galaxy with life, creating the Milky Way's diverse composition of species. Over time, they would also judge whether or not a species was worthy of the Mantle. If the species was not deemed worthy, or was found to be problematic, the Precursors would eliminate that species. Amongst the large numbers of species that they had enthralled, the humanoid species native to the world of Ghibalb, coming to be known as the Forerunners, were next chosen for this task.

This species was eventually judged to be unworthy of taking on the Mantle, and was slated for elimination. It was at this point that the early Forerunners became aware of this threat, engaged the Precursors, and succeeded in eliminating them, though a small but unspecified number managed to escape the Forerunner's campaign of extermination. Prior to their destruction, however, the Precursors had created and shaped yet another potential holder of the Mantle, a collection of humanoid species referred to as humanity, hailing from the planet known as Erde-Tyrene.


The Precursors failed to perceive the Forerunner as a significant threat; they considered them nothing more than another tool to achieve a set goal. While the Precursors acknowledged their creation's betrayal and their misguided view that they were fulfiling The Mantle, they did not wish to be driven to extinction. Before their ultimate downfall, a plan was created and put into effect by the last survivorswhich would involve a reunifying of the Forerunners and humanity to their shared origin. This plan centered on the targeted species to be subject to the Reapers, sentient, biomechanical machines created in their image and whether or not the humans would be able to overcome this foe, or ultimately succumb to it. While the Forerunner were unable to defeat the Reapers 100,000 years ago, the humans would eventually prevail, leading the galaxy as the upholders of The Mantle as originally intended.

As the Precursors hid, they surreptitiously enthralled subsequent species to erase the remaining evidence of their existence. Resigned to the Reapers' reign, they focused their efforts on ensuring the survival of their species, watching the galaxy through organic "artifacts" for signs of their discovery.


Precursor technology was extremely advanced, to the point that the Forerunners labeled it Tier 0. Some Precursor artifacts were known to precede the Forerunners by hundreds of millions of years, and were durable enough to survive being cycled inside planets' crusts by plate tectonics. Precursor artifacts were often encountered by Miners, who obtained and recorded them but rarely held any particular interest in them. The most coveted Precursor artifact among the Forerunners was known as the Organon, which was allegedly capable of activating all other Precursor artifacts.

Among the most impressive of the Precursors' structures were the enormous orbital arches and unbending filaments, which were used to connect entire worlds and solar systems. Precursor technology was amazingly durable, and was almost totally impervious to all forms of conventional damage. However, the Halo Array's energy pulse has been shown to be able to utterly destroy Precursor structures. When Charum Hakkor was used as a test bed for one of the Halos, the weapon's firing shattered every Precursor artifact on the planet. Precursor construction material was gray-silver, and would shatter along crystalline planes if broken.

Precursor technology is believed to have been based on what Forerunners called "neural physics": The concept that inanimate matter and thought are inextricably linked. It is theorized that the Halo Array, being neurological weapons, are one of the only ways to destroy or otherwise damage Precursor artifacts. This could also explain the lack of any Precursor ruins in modern society (circa 2553 CE) as most, if not all, would have been destroyed when the Halo Array fired and sterilized the galaxy at the end of the Forerunner-Flood war.