Dominion
From FEInfobase
The Dominion was a large political power based in the Gamma Quadrant. It was led by lifeforms who had the ability to shapeshift their form. They were called the Founders or Changelings by those who were not members of the Dominion.
During the Borg War the Dominion allied themseleves alongside the Federation Alliance to fight the cybernetic civilisation.
Dominion space in the Gamma Quadrant was invaded by the Borg in 2388. The Founder's Homeworld was completely destroyed and it seemed the only remaining Founders left were Odo and the Female Changeling.
The Dominion soon became members of the Federation and Dominion forces were quickly intergrated in to Starfleet.