A vast Gamma Quadrant empire ruled by the shapeshifting Founders, who command the Vorta and the Jem'Hadar.
The Dominion is an interstellar empire in the Gamma Quadrant created by the Founders, a race of Changelings who distrust solids and seek security through control. The Vorta serve as its administrators and diplomats, while the genetically engineered Jem'Hadar, bred to depend on the drug ketracel-white, form its army.
Deep Space Nine introduces the Dominion through rumours from the far side of the Bajoran Wormhole before the Jem'Hadar appear in 2370. Odo learns that he is one of the Founders, and the Dominion soon begins to infiltrate the powers of the Alpha Quadrant.
After Cardassia joined it in 2373, the Dominion went to war with the Federation and its allies, later gaining the Breen as allies too. The conflict ended in 2375 with the Dominion's surrender at Cardassia, after Odo cured the Founders of a disease and agreed to rejoin the Great Link.