Female Changeling

The Female Changeling was a highly destructive and memorable Star Trek villain who acted as the chief antagonist of the Dominion War saga in Star Trek Deep Space 9 - like many of her species she was deeply xenophobic towards non-Changelings but went much further than most in her aims of destroying them, to the point it is argued she is responsible for the deaths of billions as well as the destruction of possibly hundreds of worlds.

History
The Female Changeling assumed a humanoid form resembling that of Odo in order to greet him on his return to the Great Link in 2371. She first told him of his people, their history, and what it truly meant to be a Changeling. However, after Odo discovered his people's identity as the Founders of the Dominion, he decided to abandon the Great Link and return home.

In order to discover what was the true cause of Odo's choice to live with the solids, the Female Changeling traveled to the Alpha Quadrant and lured Odo to a deserted moon. She posed as Major Kira Nerys and forced Odo into admitting his love for the Major. She had hoped that Kira's apparent death would drive Odo back to the Link, but Odo deduced that 'Kira' wasn't real and made the Female Changeling reveal where she was being kept. Afterward she returned to the Link.

After Odo killed another Changeling, breaking their people's only law, the Female Changeling lured him home to be judged by the Link. His judgment was to be locked into humanoid form, losing his shapeshifting abilities and becoming a solid, although his face remained the same to remind him of what he had done. During her stay with Odo, she promised Cardassian citizen Elim Garak that his people would all die by the Dominion's hand.

The Dominion War broke out with the Federation's mining of the entrance to the Bajoran wormhole, trapping the Female Changeling in the Alpha Quadrant. After spending months among solids, she felt the need to be with one of her own. She sought out Odo on Dominion-held Deep Space 9. There, she linked with him in an attempt to give him a better understanding of his nature. She also manipulated him into viewing solids as inferior beings undeserving of the Changelings' compassion, time and efforts. Odo became so smitten with what the Female Changeling showed him that he began believing what she said and exhibiting similar feelings of superiority, much to the dismay of Major Kira who depended on Odo for their plans to sabotage the Dominion while they were occupying DS9. In fact, Odo was so hard in the grip of the Female Changeling that when Rom was about to be executed, he did not do anything about it but instead preferred to link with the Female Changeling.

The Female Changeling's priority was the disabling of the minefields so that reinforcements from the Gamma Quadrant could be brought in. She began overseeing Weyoun and Gul Dukat's war efforts directly from DS9. As the Dominion was eventually forced back into Cardassian space, the Founder retreated with Weyoun to Cardassia Prime, where they set up a new Dominion Headquarters. She was forced to leave Odo on DS9, but was certain he would change his mind, believing it to be only a matter of time until he saw how truly superior and better than everyone else he was and rejoin the Link.

By 2375, the Female Changeling began manifesting symptoms of a disease that had infected the Great Link - the morphogenic virus - and thus her ability to change was slowly limited; but she continued to command the Dominion from Cardassia Prime. Attempts to create a vaccine for the disease by Vorta scientists were unsuccessful. During the final months of the war, the Female Changeling's health continued to deteriorate, but she was still able to negotiate the admission of the Breen to the Dominion, which greatly strengthened their position. During the Second Battle of Chin'toka that ended in success for the Dominion, she allowed enemy escape pods to flee the battle zone so that the survivors could spread the despair and demoralization that had followed their defeat during the battle to other troops and the Federation Alliance in particular, sending a clear message to all Dominion opponents. She also had the Breen attack Starfleet headquarters on Earth for similar reasons.

Later that year, the leader of Cardassia at the time, Damar, was growing increasingly frustrated of and angry at being the Dominion's puppet and sacrificing the lives of millions of Cardassians for their cause; he realized that Cardassia had become a conquered world, forced to serve entities that had little to no regard for its interests. When he was asked to give up undisclosed amounts of territory to the Breen and make concessions that clearly went against the interests of Cardassia, he had a drastic change of attitude which eventually lead him to muster up enough courage to stage a rebellion in an attempt to free Cardassia from the shackles of the Dominion. The Female Changeling, outraged at Damar's actions, ordered that all Dominion outposts be populated by Cardassian civilians, especially women and children, so that Damar and his insurgency cells would have to kill all those innocent people first if they wanted to destroy key Dominion structures. She also specifically ordered the murder of Damar's wife and son, whom she clearly knew had nothing to do with the Rebellion, in order to teach him a lesson.

By the end of the war, the Female Changeling was so ill that she was no longer able to shapeshift. When the Federation Alliance attacked Cardassia Prime in what became known as the Battle of Cardassia, and defeat for the Dominion seemed imminent, she ordered the Jem'Hadar and Breen to fight to the last man in hopes of sufficiently damaging the Federation Alliance that it could not threaten the Dominion's territories in the Gamma Quadrant. After Cardassian civilians on Cardassia Prime began rebelling against the Dominion as part of Damar's resistance movement, she ordered every Cardassian on the planet exterminated. Members of the Cardassian resistance, led by Kira and Garak after Damar's death, penetrated the Dominion command compound and took the Female Changling prisoner. Shortly thereafter, Odo, who was present on the USS Defiant during the battle, beamed into the compound and against the protests or Kira and Garak, linked with the Female Changeling. By doing so, Odo cured her of the disease, and the Female Changeling agreed to end the war and stand trial for her war crimes. Odo returned to the Great Link to cure the rest of the Founders. The Female Changeling was taken away by Starfleet after signing the Treaty of Bajor.

In other media

 * She appears in a series of missions called "The 2800" in the MMO, Star Trek Online. She was imprisoned in the penal colony known as Facility 4028. She would be released in the year 2409, provided she assisted the Federation in stopping the Jem'hadar forces known as The 2800 and help them reclaim Deep Space Nine. After the mission was complete, she ordered the surviving Jem'hadar to return to the Gamma Quadrant with her. It's assumed that she would rejoin the "Great Link."