Kovarian

Madame Kovarian was an associate of the religious movement the Silence.

History
Frustrated by the centuries-long stalemate/conflict between the Eleventh Doctor, the Papal Mainframe and the various enemies of the Doctor during the Siege of Trenzalore, Kovarian and her followers travelled back through time to "engineer[...] a psychopath to kill" the Doctor, and prevent the siege from ever occurring. (TV: The Time of the Doctor)

Some time after Amy's honeymoon, Kovarian arranged her abduction and replacement by a Ganger. Amy's real, pregnant body was taken to Demons Run in the 52nd century. Kovarian watched over her through a hatch above the room Amy was held in. Meanwhile, her linked Ganger lived out her life. This affected the Ganger's mind. She saw visions of Kovarian wherever she went, often hearing her comments on her health and her pregnancy. (TV: A Good Man Goes to War)

The first time Ganger Amy saw Kovarian, she appeared at the little girl's bedroom door at Graystark Hall Orphanage in a hatch in the door. Amy was startled and asked who she was. Kovarian ignored her and said "No, I think she's just dreaming", then disappeared. The room was empty, with no evidence of Kovarian or the hatch. (TV: Day of the Moon)

While sleeping on a pirate ship, Amy woke to see Kovarian in a hatch that opened on the hull. She said, "It's fine. You're doing fine. Just stay calm." When Amy looked away, she vanished along with the hatch. (TV: The Curse of the Black Spot)

She was seen twice by Ganger Amy at an acid mining factory, first whilst Amy searched for Rory, though she did not speak. The next time, Amy sensed her coming appearance and stared at the wall where the hatch would open. When she mentioned this to the Ganger Doctor, who was pretending to be the Eleventh Doctor at the time, he dismissed it as "time memory, like a mirage." (TV: The Rebel Flesh / The Almost People). After her Ganger form was destroyed, Amy awoke to find herself in an alien hospital and heavily pregnant, with Kovarian looking over her. She went into labour, with Kovarian cruelly instructing her to push. (TV: The Almost People)

Madame Kovarian and Colonel Manton visited Dorium Maldovar to ask him what he knows; they had been on Yellow Alert for a month and the Doctor hadn't done anything. Dorium explained that there were numerous people throughout time and space who owe the Doctor a debt for helping them; he's gathering an army. Dorium explained the stories about the Doctor were true and not myths. Seeing they were getting nowhere, Kovarian and Manton left. (TV: A Good Man Goes to War)

At some point after Amy's baby was delivered, Kovarian took her away and had a Flesh duplicate created as a decoy for the Doctor. The duplicate and Amy were "rescued" by Rory Williams. During the battle with the Headless monks, Kovarian told the Doctor she was "privileged" to have fooled him twice in the same manner and disconnected the Flesh signal, disintegrating the duplicate. (TV: A Good Man Goes to War)

She appeared at the Luna University circa 5123 to River Song. Kovarian taunted her over her capture as a baby and her role in the Doctor's death. With Silence and soldiers from the Church, she took River and forced her into an astronaut suit with an upgraded weapons system which controlled her nervous system. River was taken to 22 April 2011 and submerged in Lake Silencio to lie in wait to kill the Doctor. (TV: Closing Time)

Alternate timeline
Kovarian was in the Area 52 pyramid in the alternate timeline created by River Song's refusal to kill the Doctor at Lake Silencio, having been captured by River and Amy Pond's military group and tied to a chair. They had created their own Eye Drives based on hers to remember the Silence, but as she told the Eleventh Doctor and his companions, the drives gave an advantage to the Silence; they could electrify them remotely, causing debilitating pain or death. The Silence began electrifying the Eye Drives, including Kovarian's. She pleaded with Amy to save her, but Amy took revenge on her for the abduction of her baby by forcibly reinserting her Eye Drive and leaving her to die. Amy remembered this after that reality disintegrated and was conflicted over her actions, although River tried to reassure her that it was an aborted timeline and didn't count. (TV: The Wedding of River Song)

Personality
Kovarian was a cruel, malevolent, sadistic, manipulative and psychotic woman who deeply hated and feared the Doctor because she believed that he would bring about the end of the universe. She took terrible glee in his anguish and humiliation. She was willing to use the Doctor's friends against him, kidnap an innocent baby and mould the child into a psychopath. She tortured Amy emotionally by kidnapping the real Melody Pond and leaving a Flesh duplicate in her place after instilling a false sense of safety when she purposefully allowed Rory to carry the fake back. Kovarian was callous, showing little concern for her allies. (TV: A Good Man Goes to War)

Kovarian was cowardly and not above pleading for her life, as shown when the Silence turned on her. She begged Amy to save her life, even claiming it was something the Doctor would do. Amy denied her any mercy, telling Kovarian that River Song had "gotten it" from her mother as well as from her. Kovarian's incredible sense of self-preservation was probably what motivated her hatred and fear of the Doctor. She occasionally showed a dry, cynical sense of humour as shown by her remark, "Oh God, do I have to watch this?" during the Doctor and River Song's flirtation. She was incredibly tactless, going so far as to beg the people she had damaged and targeted for help.(TV: The Wedding of River Song)

Behind the scenes

 * Kovarian was credited as "Eye Patch Lady" until the mid-season finale of series six, A Good Man Goes to War. Kovarian made appearances in all the stories in this first half except The Impossible Astronaut and The Doctor's Wife. She appeared under various circumstances, only to Amy Pond and always through a gap in a surface that subsequently disappeared. Her appearances acted as a story arc throughout these episodes and even with her name, little, if anything, was revealed about her.
 * Kovarian was to have a cameo in Night Terrors before the episode was moved to the second half of Series 6.
 * According to The Brilliant Book 2012, a book that contains non narrative information, Kovarian learned unspecified information from Dorium Maldovar. Kovarian later read Colonel Runaway (nê Manton)'s report on the Battle of Demons Run before demoting him to janitorial duties.
 * According to Steven Moffat in Doctor Who Magazine #473, Kovarian may have at one time been married to Tasha Lem.