The Dominion was an interstellar empire whose base is in the Gamma Quadrant and whose seat of power is located on a rogue planet on the Omarion Nebula. It was founded and led by a group of Changelings called the Founders, who over some 2000 years conquered countless worlds across the Gamma Quadrant, maintaining order through their genetically modified servitor races, the Vorta and the Jem'Hadar.
The Federation made an accidental first contact with the Dominion when Commander Benjamin Sisko, Commanding Officer of Deep Space 9, his son Jake Sisko, Jake's best friend Nog and Nog's uncle Quark were briefly captured by the Jem'Hadar in 2370 on an uninhabited class-M planet in the Gamma Quadrant. Relations between the two interstellar powers were antagonistic from the very beginning when Jem'Hadar fighter ships destroyed the Galaxy-class starship USS Odyssey, which had been sent to the Gamma Quadrant to rescue Sisko and his party.
Theoretically, the only governing body in the Dominion are the Founders, who hold the decisions that affect the destinies of hundreds of races. In practice, the Founders do very little governing, content to remain on their homeworld isolated from the Known Galaxy. Only during times of great turmoil have they had an active hand, the latest being when Odo was revealed to them. This began the chain of events resulting in the Dominion War.
The ruler of the Dominion is a Vorta who serves as the Prime Jeddak, which roughly serves as an emperor. Immediately beneath him is the Supreme Council, consisting of sixteen individuals that manage various programs within the Dominion, such as diplomacy, war, colonial affairs, and media. For citizens, there is no illusion that power lays anywhere other than the Prime Jeddak and Supreme Council. However, a legislative body known as the Citizens' Parliament exists, nominally to resolve disputes between member worlds.
Law and order
The thousand worlds who are members of the Dominion are treated equally before the Founders. Because of this, there are few restrictions on governing for homeworlds. Members can be as dictatorial or democratic as they wish, merely agreeing to provide taxes to the Dominion in exchange for protection and trade benefits. On each member world is a council of five Vorta, appointed by the Citizens' Parliament, to oversee affairs and provide counsel to the world's leaders, but otherwise have no direct influence in governing. In addition, each world has a full regiment of Jem'Hadar shocktroopers, who are kept on standby in the event of a planetary disaster or political uprising.
The culture of the Dominion is dictated by the worlds within it. The more widespread races, such as the Vorta and Wadi, have had much more influence than others. A quadannual handball competition known as the Ludian Tournament is one of the most, if not the most, anticipated events within the Dominion.