Symbiote (All Tomorrows)

The Symbiotes were a posthuman species that evolved from the Parasites. Many of the parasite species and their hosts evolved from a parasitic to a symbiotic relationship, with the symbiotes offering their hosts heightened senses in exchange for their blood.

This lead to a kind of arms race where many species of symbiotes and hosts developed, each having different biological weapons and advantages making them attractive for each other. There were symbiotes with extremely efficient eyes and noses or venomous saliva, and hosts with long running legs, strong bodies or specialized heads with more blood vessels and insulating fur for symbiote nesting. Many species of symbiote were only compatible to certain species of hosts.

In one forest area, there evolved a species of symbiote that didn't have any biological weapons, but extremely efficient brains. They developed sapience and controlled their hosts like riders, and over time they began to totally dominate their hosts through tactile and olfactory signals.

This symbiote-host-civilization developed countries, fought wars and eventually led to a globalized culture. They also developed technology which could do some of the things that hosts previously did, but they still used hosts out of tradition and efficiency. A single symbiote often had different hosts for different tasks.

Some of their technologies was olfactory television and radio listening to signals from space. They also excavated ruins of the Qu and Star People and found out about their heritage, which led to them joining the Second Galactic Empire founded by the Killer Folk and the Satyriacs as part of the third wave of newcomers.

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 Symbiotes and their hosts, along with all of their cousins, were quickly wiped out by the Gravital as part of their interstellar conquest.