The Great Assimilation, often referred to as "The Council" after one of their two governing bodies, or TGA, is an inter-universal empire started in the 10,000 Dawns. The Great Assimilation is ruled by The Three Emperors, two humans and an alien, as well as a vast council made up of it's many member peoples. The Great Assimilation, unlike most groups inside the 10,000 Dawns, has no reservations about expanding outside it.
TGA is an extremely cosmopolitan culture, accepting anyone into their group as long as they are willing to submit to their government, and assimilate into their society. "Assimilation" is their most important virtue, with every member group adding something new and good to the collective whole, while taking on parts of TGA that benefit them, at least according to what the Council thinks is best for them.
Members of the TGA military have often been seen wearing black and gold uniforms.
Agents of TGA were present at the auction of the Book of Books in the Whoniverse where they offered the Strid a planet and place in the Assimilation in exchange for the book. The auction was thwarted by Rachel Edwards, however. (Rachel Survived)
Around 2502, the Great Assimilation invaded the Prime Universe in an attempt to take over the 10,000 Dawns, their reasons for this are unknown, but their agents claim benevolence. (Death and Doubling Cubes)
Memnor was the leader of it's Intelligence Agency during their Incursion into the Prime Universe.