Thrintun hadn't needed intelligence since they'd found their first slave race.

His men came from a slave race, and they dreamed of a day when they would be free.

One day the slave races decided they'd had enough, and there was a war.

"Do you doubt that a slave race in revolt would settle for nothing less than our total extinction?"

They created the shoggoths to be their all-purpose slave race.

A slave race that knew that all things must change.

It is also revealed that any species within their empire are slave races.

This is to keep a slave race of aliens called Sequids from rising up.

Now they're attacking throughout known space with half a dozen slave races.

This was major news, given that the Remans had, up until now, been a slave race within the empire.