So far as Paramount/CBS novels go, I remeber there being a power called the Regnancy of the Carnelian Throne present in The Buried Age
. I'm not sure off-hand if they had a primary species "in charge", of if they treated each of their member/slave species equally.
The premise behind the Regnancy of the Carnelian Throne was that it had evolved out of an older kingdom whose monarchy had been effectively but not legally ended; it had originally enslaved other species, but eventually the oppressed races ended up in effective control of the government. The original species of the Regnancy was forgotten, but the interstellar union they had created lived on. The formerly-oppressed peoples, however, kept the nomenclature of "slaves," with the idea being that their true master was no mere person or government, but the ideals of peace and justice. Anyone who did not consider himself a "slave" to peace and justice was someone the Carenlians did not trust.
The depiction of the Regnancy was inspired by a single line from TNG, where Picard describes seeing Natasha Yar for the first time while she's dodging a Carnelian mine.