Aphasia

Aphasia, also known as Daughter of Mine or Sister of Mine, was a creature which took on the appearance of a human girl and whose story had happened "many times in many different ways", some of which she hadn't even been "present for" and only learnt about while viewing them through mirrors. (AUDIO: Shadow of a Doubt) In one of these, she was an Aubertide; (PROSE: Human Nature) in another, she was a member of the Family of Blood. (TV: The Family of Blood)

One version of Aphasia menaced the Seventh Doctor and Bernice Summerfield on Earth in 1914 when she and her family attempted to gain his biodata and become Time Lords - complete with psychic powers and regenerative abilities. This version was shot and killed by students during an attack on Hulton College. (PROSE: Human Nature)

Another version was the daughter of a criminal family known only as the Family of Blood, who led an attack on Farringham School for Boys in 1913, hoping to steal from the Tenth Doctor a means of attaining immortality. When the Doctor caught her after her family tried to take his life force, he trapped her inside every mirror in existence. He visited her once a year, every year, (TV: The Family of Blood) across several incarnations, including the Seventh Doctor, the Twelfth Doctor, the thin white aristocrat, the wheelchair-bound Doctor, (AUDIO: Shadow of a Doubt) and the redheaded Doctor. (AUDIO: Shadow of a Doubt, WC: The Shadow in the Mirror)

On Andromeda, Bernice encountered Daughter of Mine and identified her as Aphasia. Bernice refused to free her from the mirror until she apologised for her actions, but Daughter of Mine attempted to insist that Aphasia had been a "different her". Bernice didn't believe the excuse and abandoned the mirror. (AUDIO: Shadow of a Doubt) Eventually the Thirteenth Doctor returned to free Daughter of Mine, despite her voicing her plan to continue killing lesser beings, and took her back to her homeworld. (WC: The Shadow in the Mirror)

Biography
The daughter of Serif and mother of Hoff, Aphasia was an integral part of the Dubraxine family and joined them on their assault of Hulton College in their attempt to locate John Smith (who was in fact a human identity created by the Seventh Doctor) and obtain the biodata pod containing his Time Lord DNA. During the assault, students led by Rocastle shot and killed Aphasia. Enraged, the rest of her family followed custom and ate her entire body before using a fusion bomb to turn the entire school to glass as a tomb for her. (PROSE: Human Nature)

Another version appeared to be the youngest member of the Family of Blood who joined them in chasing the Tenth Doctor and Martha Jones through time with a stolen vortex manipulator. When they arrived on Earth in 1913, she possessed the body of Lucy Cartwright and infiltrated the dance hall where she worked out that John Smith was the Doctor. The Family's quest for immortality ended when the Doctor was returned to his Time Lord state and destroyed their ship, he punished each member of the Family individually — trapping the daughter within every mirror in existence. Her Brother wondered if one day the Doctor would forgive her.(TV: Human Nature/The Family of Blood)

The Tenth Doctor deduced that the Mortal Mirror wasn't a real mirror because "a girl with a red balloon" wasn't inside it. (PROSE: Martha in the Mirror)

Freedom from the mirrors
According to one account, Daughter of Mine managed to escape her imprisonment by possessing Nancy Latimer, and set her father and brother free as well. To free Mother of Mine, they captured the Doctor and Donna Noble in the TARDIS, but the Doctor managed to escape his restraints and trapped the entire Family of Blood with Mother of Mine in the black hole, after freeing Nancy from possession. (PROSE: Blood Will Out)

According to another account, Bernice Summerfield discovered Daughter of Mine in a mirror on Andromeda but, like the Doctor, refused to release her until she apologised for her crimes. (AUDIO: Shadow of a Doubt) On Calapia the Thirteenth Doctor thought back to putting "this girl in a mirror" and decided to finally release her, claiming that it no longer suits who she is. (PROSE: The Shadow Passes) She did this on her first visit to the girl, returning her to her home planet. (WC: The Shadow in the Mirror) Bernice later returned to Andromeda to find Daughter of Mine and the mirror missing. (AUDIO: Shadow of a Doubt)

Daughter of Mine appeared as an exhibit within a museum created by Es'Cartrss that existed inside the TARDIS Matrix. (COMIC: The Forgotten)

Alternative timeline
An alternate timeline glimpsed by Timothy Dean showed a possible future of a Gallifrey overtaken by the Aubertides should they succeed in gaining the Doctor's Time Lord DNA. In this timeline a statue had been erected in memory of Aphasia, but this was ultimately averted when John Smith helped the Doctor to become himself again. (PROSE: Human Nature)

Appearance
Two of her known versions opted to appear as a young girl with a balloon (PROSE: Human Nature, TV: Human Nature/The Family of Blood) Both of these versions were shown to be able to command the balloon to pursue and kill people (PROSE: Human Nature, WC: The Shadow in the Mirror) When Bernice Summerfield popped the balloon, one Aphasia fell screaming in pain. (PROSE: Human Nature) The same version of Aphasia had a hidden pouch in her wrist where she concealed black capsules that released lethal gas. (PROSE: Human Nature)

The guise of a little girl meant that she was able to infiltrate places, such as the dance hall and the Farringham School for Boys. Despite this, Lucy Cartwright's parents sensed that something was off about their daughter, but were apparently murdered by her before they could impede the Family's plans.(PROSE: Human Nature, TV: Human Nature/The Family of Blood)

Personality
Aphasia was psychopathic, and desired to look into the Time Vortex so that she could see horrible things. (PROSE: Human Nature) While as Daughter of Mine she possessed a similar interest with looking at the Doctor's essence inside the fob watch but fled in terror upon witnessing some of the Doctor’s darker moments. (TV: The Family of Blood)

The original version of Aphasia hated gargoyles, and was known to be interested in watching Greeneye's sexual conquests. (PROSE: Human Nature)

While rarely speaking, Daughter of Mine displayed a cold, detached and remorseless personality. She was just as murderous as the rest of her family and did not hesitate to kill Lucy Cartwright’s parents or Rocastle and even coldly stated that she found killing people “funny”. (TV: Human Nature/The Family of Blood)

Behind the scenes

 * The television adaptation of the novel Human Nature replaced the Dubraxine family with the Family of Blood, with only Daughter of Mine retaining the appearance of her counter-part Aphasia. However, the in-universe relationship of the two characters was confirmed in the webcasts Shadow of a Doubt and The Shadow in the Mirror which follows on from the television stories directly references events from the novel, stating that Aphasia and Daughter of Mine are "different versions" of the same individual.
 * It was originally intended for Daughter of Mine to be transformed into a sentient statue in a shopping precinct at the end of The Family of Blood but this was changed due to the next episode Blink heavily featuring living statues.
 * Daughter of Mine is one of the enemies in Legacy mobile game.