Little is known about the mysterious Precursors (as humanity calls them). Ancient artifacts and ruins have been found scattered across the galaxy but no sign of a living civilization has ever been found. It is thought that they were once an advanced space-faring race who influenced the development of over a dozen worlds and connected many of the galaxy's solar systems together with the jumpgate network, then for some reason they vanished about 5,000 years ago. It isn't known whether they were wiped out through war or disease, or simply chose to leave. There are dozens of theories about what happened to them and religions have sprung up surrounding each one both in worship and in fear.
One of the most famous Precusor artifacts (for humanity at least) is the Azure Spire, a 10 meter tall glowing blue spike excavated from the New Arizona Desert. It is the only piece of Precursor technology discovered on Earth and led to a century of rapid technology development as scientists disassembled it. Inside it was made of a previously unknown form of circuitry, microscopic organic lattices interwoven with incredible complexity and density. A single cubic inch contained more technology than a thousand Earth computers.
Although much was learned about science and technology in general, the purpose of the Azure Spire remains a mystery.
A more significant find awaited humanity on the edge of their solar system: the jumpgate.
These ancient artifacts are huge circles of carbon alloy, each one about the size of Earth's moon. They are commonly found orbiting at the edge of solar systems and provide transport from one to another across the incredible distance of space.
Humanity is not the only race to encounter the remnants of the Precursors however, their relics have been found on many worlds and each of the known sentient species has had at least some experience with them. The Chanor found a ruined structure on one of their three moons. The Ortani found a ruin at their planet's icy northern pole and also claim that their ancestors were once experimented on by the Precursors. They believe that these experiments granted them their unusual psionic abilities, although there is limited evidence to confirm this. The Sygarians discovered their planet was orbited by 12 spherical precursor satellites, which they call the Eyes of the Ancients. These artifacts have since been captured and disassembled for study, although several can be found in museums.
It isn't know what experience the Veratha have had, they remain always aloof and mysterious, rarely talking to the other races at all. Some have suggested that maybe the Veratha are the Precursors but most scientists dismiss this notion due to the apparent differences in their technology (although there has been little opportunity to study Veratha technology).
Since leaving their home world, each species has discovered ruins and artifacts scattered across the galaxy, some found on dead worlds, others located on asteroids or moons. Neither a living specimen, nor a dead body has ever been found that can be confirmed to be precursor, in fact no one knows what they look like.
Most recently an Earth probe sent to the Antares system detected the largest Precursor ruin ever encountered by any species, the only one that can be said to be a city. The ruin is located on the 4th planet from the star, leading to the attempted illegal colonization by the SS Daedalus.