The Female Changeling was a Founder from a rogue planet located in the Omarion Nebula, in the Gamma Quadrant. She was chosen by the Great Link, a giant gelatinous sea of shapeshifters, to represent the interests of the Changelings in both the Gamma and Alpha Quadrants and instigated a bloody, genocidal interstellar war in order to conquer their inhabitants and worlds and subjugate them to the rules of the Dominion: a major galactic political power established by the Founders to defend their interests at all costs. The Female Changeling harbored a particular mistrust and hatred towards non-Changelings - whom she referred to as solids - believing them to be infinitely inferior and unworthy beings by design.
She was trapped in the Alpha Quadrant during the start of the Dominion War and helped coordinate the Dominion's war efforts, ultimately leading to the destruction of hundreds of worlds and the death and suffering of hundreds of millions of people.
The Female Changeling ultimately paid the price for the millions of lives lost when Starfleet forced her to sign the Treaty of Bajor that ended the war and took her into custody.