Tool Breeder

The Tool Breeders were a posthuman species that evolved from the Swimmers.

Without the possibility to use fire, the Swimmers always adopted other species symbiotically to use them. In this way, they domesticated some creatures even before fully evolving sapience.

Later, this evolved into full fledged genetic engineering, with the tool breeders creating everything they need for their daily life from other lifeforms or later from stem-cells.

Their technological advances include: During the following ten million years, other posthumans joined in on the communications, including the Modular People, Pterosapiens and Asymmetrics. After another 20 million years, the empire also included the Saurosapiens, Snake People, Symbiotes and the Sail People. Only after fourty million years, the Bug Facers joined in.
 * Heart-like creatures that pump nutritional fluids into living buildings and machines
 * Shell-like buildings
 * Bio-luminescent lights
 * Cephalopod skin-televisions
 * Medical sea-squirts
 * Oxygen-filtering crustaceans for breathing under water
 * Mollusk-derived rifles that shoot out specially-modified "bullets"
 * Brain-augmented hunting-fish hardwired to return kills
 * Living starships
 * Living radio arrays, through which they made contact with the Satyriacs and the Killer Folk.

Over a timespan of about 80 million years, the Second Empire developed, through the combined effort of all members, into a galaxy-spanning empire, even though the members never met each other personally, and all of the species colonized other planets.

Though they were prepared to face an alien invasion, the Empire didn't think about an invasion from other posthumans, and so the Tool Breeders, along with all of their cousins, were quickly wiped out by the Gravital as part of their interstellar conquest.