Born Moira Kinross to Scottish parents, Moira MacTaggert was one of the world's leading authorities on genetic mutation, earning her a Nobel Prize for her work. She was the longest running human associate of the X-Men and was Professor Charles Xavier's colleague, confidante, and also once his fiancée, having met and fallen in love with him while they were postgraduates at Oxford University. She ended their engagement when for reasons unknown she married her old flame, the late politician Joseph MacTaggert. Joe proved to be an abusive husband; Moira separated from him after he beat her into a week long coma and, as it is implied, raped her, leaving her pregnant. She kept her son's existence a secret, and when Joe refused her a divorce she allowed people to believe she was widowed. She eventually created a Mutant Research Center on Muir Island, off the coast of Scotland. Moira was forced to contain and imprison her son Kevin, later called Proteus, when he developed reality warping abilities and severe psychosis. One of Moira's goals was to understand human/mutant genetics, in order to cure her son. Moira's connection to the X-Men began long before the team formed. The silent partner in the founding of Xavier's School for Gifted Youngsters and co-creator of Cerebro, Moira assisted Xavier in helping the young Jean Grey recover after the traumatic triggering of her mutant abilities. Moira was a kind woman who took to helping humans and mutants alike. She rescued a young, Rahne Sinclair, from an angry mob, and adopted the girl. She even attempted to treat Xavier's son, a mutant known as Legion who suffered from multiple personality disorder. When Cable arrived from the future, it was Moira who taught him English and introduced him to Xavier. When Magneto was reduced to infancy, he was entrusted to Moira's care on Muir Island, where she altered his genetic code in an attempt to keep him from reverting to villainy (an unethical decision that she believed was for his benefit).
Involvement with the X-Men
The X-Men first met Moira when she appeared at Xavier's call to act as "housekeeper" for the team while they were on missions (a position that required her to demonstrate her proficiency with an M16 rifle within hours of her arrival). Though each of the X-Men formed some sort of relationship with the "Widow" MacTaggert, Moira and Sean Cassidy hit it off immediately, forming an on-and-off relationship that would last for the remainder of her life (ironically, before meeting her, Sean had assumed she would be "eighty years old, ugly as sin" and received the shock of his life when he saw the attractive young lady for the first time). Proteus's escape and eventual destruction at the hands of Colossus and the X-Men left Moira in a position of ethical compromise again: though Banshee stopped her from cloning her son, she saved his genetic structure on disk to allow herself the future option of bringing him back. After finding out that her foster daughter, Rahne, was a mutant, Moira was the catalyst for change. She talked a discouraged Xavier into opening his school to the next generation of New Mutants, with Rahne becoming an initial member. She was also an integral part of the support for the X-Men and the New Mutants, providing medical aid including cloning Xavier after the Brood attacks, restoring his ability to walk. With the apparent death of the X-Men, Moira and Banshee formed an alternate team based from Muir, and carried on as the leader of the team without him when his duties with the X-Men called him away. Her behavior became unpredictable, her temper impressive, and her decisions harsh and unforgiving as she displayed behavior that made all who knew her suspicious. On Muir, she began to pit her charges against each other in an arena in merciless battles, supposedly allowing her the opportunity to study mutants in action. Eventually, the entire population of Muir Island was identified as being possessed by and mentally corrupted by Shadow King, pitting the Islanders against the combined forces of the X-Men and X-Factor before Xavier freed them from his control. Moira's alteration of Magneto did not go unnoticed indefinitely. Enraged when he discovered Moira had tampered with his free will, Magneto took Moira captive and forced her to perform the procedure on half of the X-Men, turning them against their teammates. While Moira's alterations worked, it was revealed that when activated, the X-Factor gene that gave mutants their powers reversed the effects of the procedure, so anything Magneto had done was of his own free will. While hostage on Asteroid M, Moira witnessed Fabian Cortez draining Magneto of his powers and manipulating him into placing him as his right hand. Though Cortez fled, it was an observation that would eventually put Moira back in the hands of the Acolytes. Back on Earth, Moira was unable to accept her betrayal of her surrogate family and her own infallibility, and fled the X-Mansion, with Banshee in pursuit.
Excalibur and the Legacy Virus
When a mysterious virus began attacking the genetically engineered mutate population of Genosha, Moira volunteered her services as a geneticist and was forced to watch as the former slaves were decimated by disease. Returning to the X-Mansion, Moira found Illyana Rasputin suffering from the same illness, later identified as the Legacy Virus. Moving back to Muir Island after the girl’s death, Moira became the key figure in working for a cure to the disease. (During this time she also worked on curing Wolfsbane's artificial bond with Havok). The European superhero team Excalibur took up residence on Muir Island after assisting Moira. She had been attacked by agents of Mister Sinister who was seeking the genetic information on her son. Moira became an official member of the group, acting as their medic, team mother, and morale officer. An information leak revealed her to be the only human infected by the Legacy Virus—a bizarre turn of events possibly caused by her long exposure to the infected on Genosha, her autopsy of Illyana, or some susceptibility because she gave birth to a mutant. Despite these events, she maintained a strong outlook on life, helping to maintain discipline, reduce tension, and increase the team's effectiveness throughout Europe. She convinced the team to stay behind when Onslaught emerged, telling them they might be needed if other heroes fell. Conferring with the X-Men's Beast did not result in appreciable progress. Locking herself in quarantine in a final attempt to cure the virus without endangering any of her teammates, Moira found her attempts foiled by her foster daughter Wolfsbane and Douglock. Wolfsbane originally leapt through the closing doors of the laboratory as the quarantine took effect. She soon found herself a willing assistant to her foster mother's work. Douglock later caused much unintentional damage, his judgement clouded by personal feelings for Wolfsbane. Moira did eventually find a cure for the disease, when the terrorist Mystique manipulated her research to force the virus to target only humans. Mystique, partly assisted by Sabretooth, then destroyed Muir Island, de-powered Wolfsbane, and brutally injured Moira. Bishop, Wolverine, and Rogue attempted to save Moira's life. Despite Rogue's powers temporarily granting her medical knowledge, she was unable to do so. She clung to life long enough to mentally transfer the information to Xavier in one final embrace between the former lovers. She died in the X-Men's jet, far above the Atlantic Ocean, and was later buried in Scotland. A psychic representation of Moira was seen as an active portion of Xavier’s consciousness as he worked on rebuilding Genosha. Her ghost has also been seen in the rubble of Muir Island, directing Banshee to a hidden room full of video files. Moira is next seen in the afterlife , in which she, Mockingbird, Gwen Stacy, and Dead Girl assist Doctor Strange in battling a being known as the Pitiful One.
X-Men: Deadly Genesis
After the events of M-Day and upon the reawakening of Vulcan, significant portions of Moira's history with Xavier and the Original X-Men is called into light. During the early years of Xavier's Academy, Moira founded and ran a secondary facility not far from the Xavier School, in which she had her own students; youths who she took out of bad situations and adopted as her wards, training them in their abilities without the highly militant regimen of Charles' X-Men. When Krakoa captured the original X-Men, it was Moira's students whom Charles went to first—not the second team of Wolverine, Storm, Banshee, Colossus, Nightcrawler, Thunderbird and Sunfire as it was originally believed—putting them through the psionic equivalent of boot camp and allowing them to believe they were being trained over months as X-Men. Charles took them from Moira's care immediately. Moira's students: Vulcan (Gabriel Summers, the lost brother of X-Men Cyclops and Havok), Petra, Darwin, and Sway—were apparently all killed, and Xavier suppressed even the memory of them from his own students, to keep them from going back to save them. Only Moira's project tapes, one made directly after the event before Xavier could suppress the memories, and an abandoned research center remain as clues.
Dr. Moira MacTaggert was one of the world's leading geneticists and possessed special expertise in the study of superhumanly powerful mutants.
Moira MacTaggert possessed the normal human strength of a woman of her age, height, and build who engages in moderate regular exercise.
Moira accidentally genetically engineered a child using some of Xavier's blood that she was examining when she accidentally dripped her own blood (as she was bleeding from a cut) in the sample. The child was a boy who Moira had to give up immediately because she could not deal with parenthood and believed that Xavier would never heal. Moira was so wracked with guilt over giving up the child that she broke off the engagement.
Moira was the butt of a recurring joke about her coffee being too bad-tasting; even Xavier mocked her about it sometimes.