The Precursors are an ancient race of ottsels and the central deities of the series' setting. Due to the Precursors being small, rodent-like ottsels, they fabricated a mythos of large, god-like creatures made of Precursor metal, humanoid in stature with insectoid heads, large round eyes, and a proboscis extending below their jaw. This was perceived as the Precursor race's appearance for most of history before their discovery by Jak and Daxter towards the later parts of Jak 3, in which they were revealed as ottsels. Despite their appearance, they are still the "most powerful beings in the universe." Although all known Precursors are ottsels, and all known ottsels are Precursors, it is unknown if all ottsels are necessarily Precursors.
In the games' mythology, the Precursors created Jak's planet, apparently as well as many others. They created and used a substance called eco to create many of the world's environments, as well as Precursor metal which they used to create large pillars, constructs, and other massive structures, which outlasted and predated all artifacts known to humans during the series' events, and were referred to as Precursor artifacts. At some point early in the Precursor civilization, the Precursors were opposed by the Hora-Quan and the Dark Makers (Although when they were opposed, and in what order remains largely unknown). It is revealed that the Dark Makers were actually once Precursors, but were corrupted by the uncontrollable dark matter known as dark eco. The Hora-Quan were a biomechanical alien race which was said to have wiped out most Precursor civilization and ruled the universe unopposed. When the Precursors created Jak's planet, they created an eco core which stabilized the distribution of eco in the world, as well as the Planetary Defense System, which was a massive weapon powered by eco crystals, should the threat of the Dark Makers approach.
At some point during the creation of Jak's planet, the Precursors stopped building at the Brink, and fled to the Precursor core so they could manage the Planetary Defense System. They left behind various artifacts and relics, including oracles and idols which they used to communicate with the world's inhabitants, particularly Jak.
The Precursor Legacy
Who were the Precursors? Why did they create the vast monoliths that litter our planet? How did they harness eco, the life energy of the world? What was their purpose, and why did they vanish?Samos Hagai, The Precursor Legacy
During the time of The Precursor Legacy, the Precursor's origin and discovery of their secrets through Precursor artifacts was a major theme. Precursor artifacts and relics could be found all over the world's environment, and clusters of eco were plentiful, as well as ancient Precursor pipelines which would freely release eco out into the world through eco vents. There were numerous locations littered with Precursor technology such as Forbidden Temple, Misty Island, lost Precursor city, Precursor Basin, Snowy Mountain.
The Precursors themselves weren't prominent during this game, although they did speak to Jak through the use of oracles. These oracles would task Jak with bringing them a certain amount of Precursor orbs in exchange for power cells. They would also speak prophetically and cryptically hint at the series' plot.
Similar to the first game an oracle statue could be found, and would task Jak now with bringing the skull gems of metal heads (what the Precursors refer to as the Hora-Quan) in exchange for control over dark powers.
Also revealed in this game was the Precursor's ancient connection with Mar, an ancient and legendary warrior said to have founded Haven City and built a massive weapon intended to destroy the Metal Head nest. His weapon could only be powered by the last Precursor Stone, an egg-like object said to contain one of the last Precursors. Towards the end of the game, the Precursor Stone was activated by "the Kid" (younger Jak before his purity was defiled by dark eco experiments) and a ghostly Precursor figure was released and traveled through the active Rift Gate for the "ancient race to begin again."
Don't let our size fool you. We are the most powerful beings in the universe.Ottsel Leader, Jak 3
During Jak 3 an even higher proliferation of oracles were revealed, as well as Precursor Monks who studied and worshiped the Precursors in their Monk Temple. Precursor technology was much more prominent during this time than in Jak II, as the catacombs were finally discovered, ancient high speed tunnels leading to the Precursor core (Where the last Precursors were said to be located) as well as the Planetary Defense weapon. Throughout the game the Dark Makers approached Jak's planet, making the Precursors' assistance, prominence, and eventual appearance expedient. More Precursor projections similar to what emerged from the Precursor Stone in Jak II appeared, now giving Jak the use of light powers as well as dark powers. Before the Precursors were finally shown and revealed, Seem made a vague but interesting implication of their physical appearance when they say that Daxter carried the color of the "creators".
Towards the end of the game, when Jak, Daxter, and Veger arrive at the Precursor core, an off-screen squabble caused the door to the core to open, revealing three ottsels: Ottsel Leader, Ottsel Surfer, and Ottsel Dummy. At first Veger accused the ottsels of "defiling" such pure Precursor technology, though after Veger was pinned up by the Ottsel Leader's staff, it was revealed the ottsels were in fact the Precursors. The Ottsel Leader explained that they "fluffed up the myth a bit" to be revered and worshiped as gods instead of as rodents, but they still remained the most powerful beings in the universe.
Eventually the three Precursors left Jak's planet after the threat of the Dark Makers was nullified by Jak. They took off in a space shuttle, offering to take Jak with them, though he apparently declined.
To hide their true forms as ottsels, the Precursors created the myth that were large humanoid figures with a round head and insectoid eyes, and a large proboscis extending from their jaw which was used sometimes as a weapon or dispenser of eco.
Due to their control over eco, they could produce eco in places there was once none, though this ability is seen only where eco is already made (the eco core), and they can imbue people with the power of eco. They can also turn people into ottsels like themselves and detain people, as seen when Veger tried to question the Precursors' power, and even create clothing for those they turn into ottsels.
The exact society of the Precursors remains unknown. The only Precursors seen in the series were the three ottsels, though it was made apparent there were more. They created various scripts, one of which was used heavily throughout the series known as the Precursor alphabet.
The best-known weapon created by the Precursors is the Precursor robot; a massive metal humanoid, armed with lasers, missiles, bombs and an incredible endurance. Other examples include the dark eco canister, the very first artifact seen in the series, although it isn't clear whether this was originally created as a weapon. The Planetary Defense System appears to be one of the older Precurian weapons in game, as it presumably came together with the Catacombs, and was powerful enough to destroy the Dark Maker ship on its own during the events of Jak 3.
The only seen Precursor vehicles seen are the Catacombs rail rider and the space shuttle. They are known to have used teleport gates to travel, and it can be assumed they had networks of interlinked teleport gates. They also use Rift Gates, which were used to travel in time, although all of these known to humans have been destroyed.
Well-known devices are the teleport gates, power cells, precursor orbs, and Precursor staffs. Perhaps the most story-relevant device is the Rift Gate, the time-travel device that brought Jak, Daxter, Samos, and Keira to the future (and later a younger Jak back to the past). Aside from these there's also the oracles, used to communicate with the world's inhabitants.