In 2371 Odo found his people on a world in the Omarion Nebula and learned they were the Founders, the rulers of the Dominion.
After the Dominion's warning, Starfleet assigned the warship USS Defiant to Deep Space Nine, and in 2371 Sisko took it into the Gamma Quadrant to seek talks with the Dominion's leaders. Odo felt a pull toward the Omarion Nebula, where he and Kira found a world of shapeshifters like himself.
The changelings revealed that they had been persecuted by solids long ago and now ruled the Dominion as the Founders, controlling the galaxy through order. They had sent infants like Odo out to learn about other species. Odo rejected their ways and returned to Deep Space Nine.