Yuht

The Yuht is a long-forgotten precursor race that existed in the galaxy six million years ago.

Biology
The Yuht were a sapient race of large centipede-like insectoids. Each individual Yuht can reach hundreds of meters long. Due to this, Yuht spaceships rarely carry more that three passengers. The Yuht had an extremely low birth rate and would dedicate whole worlds for breeding. They do this by sterilizing predators and other harmful species before laying their eggs. They would then leave their young to fend for themselves until the parents would return to reintegrate them in Yuht society. An average Yuht could live up to a thousand years so every death was treated as special event in Yuht society. At every funeral the dead are buried with lavish gifts.

History
Approximately six million years ago, the Yuht started colonizing star systems near their homeworld. However, the Yuht never discovered Faster-Than-Light (FTL) travel, which meant that interstellar travel often took centuries. The Yuht relied on their thousand-year lifespans and cryo chamber technologies to spread their species across the galaxy.

For two million years, the Yuht have never encountered any intelligent life and assumed that they are the only sapient race to have ever existed in the galaxy. Over time this made them feel superior and decadent to the point where they are rarely making any more scientific discoveries. At some point, Yuht scientists came across ancient artifacts which could prove that intelligent life existed at some point, but they quickly dismissed them as a fraud and stored them in a museum dedicated to "disproving" such a theory.

The Yuht were eventually proven wrong when they encountered the Jabbardeeni, a far younger but sapient race, who recently managed to achieve interstellar travel. This discovery came at a tremendous shock for the Yuht. Feeling that the Jabbardeeni is a threat to them, the Yuht decided to eradicate them before they become too powerful. The Yuht launched a surprise attack on the Jabbardeeni homeworld. The Jabbardeeni managed to put up a stiff resistance, and eventually the invasion failed.

Meanwhile, the Jabbardeeni began discovering technologies unavailable to the Yuht, including FTL travel, allowing them to gain the upper hand in the ensuing war. The Yuht's extremely low birth rate and small numbers proved to be their undoing, as many Yuht were killed. But what really crippled them is the lack of any sort of FTL technology despite being around for millions of years longer, owing to their arrogance and stagnancy. In less than a decade of war, the Yuht were utterly destroyed, marking an end to the two-million-year-old civilization.