Founder

From Memory Alpha, the free Star Trek reference.

The Founders were a group of Changelings from the Gamma Quadrant. Though generally considered mythical, they were the ruling force behind the Dominion. (DS9: "The Jem'Hadar", "The Search, Part I", "The Search, Part II")

At one time the Founders were a peaceful, curious race that explored the galaxy, possibly including L-S VI. (DS9: "The Alternate") Unfortunately, their overtures of peaceful cooperation were met with violent rejection and persecution. As an adverse reaction to being hunted and rejected, they accepted the pejorative Changeling as their own and retreated to a rogue planet. They then determined that, in order to be safe, they must set themselves the task of creating order from the chaos they saw around them.

What you control can't hurt you. - Founder (DS9: "The Search, Part II")

The solids have always been a threat to us; that's the only justification we need. - Founder (DS9: "The Search, Part II")

Chaos was dangerous as it would allow the persecution to arise once more. Therefore they must have order but this was an order that they controlled, for their benefit and only incidentally for the benefit of the "solids."

Once they consolidated their control they sent out a number of their kind across the galaxy to learn more about any other solids. The two most notable of these lookouts were later known as Odo and Laas. The mission of the lookouts was to learn as much as possible about the solids in their area, and report back. (DS9: "The Search, Part II", "Chimera")

See also: Dominion history

As the leaders of the Dominion, the Founders lead a vast Empire, with the assistance of two genetically-engineered species, the Vorta, to whom they delegate the day-to-day work, and the Jem'Hadar, to whom they delegate most military matters. Both species consider the Founders to be gods. (DS9: "Hippocratic Oath", "Tears of the Prophets")

[edit] Background Information

Although the concept of the Founders had been established in the DS9 second season finale "The Jem'Hadar", the writers hadn't made any firm decisions about who the Founders were. During the hiatus between season two and three, Michael Piller called a production meeting and, thinking the writers would reject the idea straight away, he suggested that perhaps the Founders could be Odo's people. When Piller suggested this, Ira Steven Behr burst out laughing, as he and the other staff writers had come up with the exact same idea, but they didn't think that Piller would accept the proposal so they hadn't pitched it to him. (The Birth of the Dominion and Beyond, DS9 Season 3 DVD, Special Features)