Katherine "Kitty" Pryde was a 13½-year old Jewish girl whose genius level intellect allowed her to take college-level courses despite her young age. Kitty led a fairly normal life until she began suffering headaches of steadily increasing intensity, which were a result of her emerging mutant power.
Kitty herself was unaware that she was a mutant until the afternoon that Emma Frost, then White Queen of the Hellfire Club, arrived to speak to her parents about enrolling Kitty in her Massachusetts Academy. During the visit, Kitty suffered her worst headache yet and went upstairs to her room. When the headache stopped, Kitty was surprised to find she was on the floor of her living room. She had unknowingly used her power to phase through solid matter for the first time, passing through her bed and floor into the room below.
After Frost left, Professor Charles Xavier arrived with three of the X-Men, his own team of mutant students who fought for peaceful coexistence between humans and mutants. Following an attack by the Hellfire Club during which Kitty helped the team, the X-Man Phoenix telepathically coerced Kitty's parents into allowing her to join Xavier's school, and she became the newest and youngest member of the X-Men. Kitty originally called herself Sprite, but later adopted the codename Ariel. Xavier also arranged for Kitty to be enrolled in dance classes at the studio of instructor Stevie Hunter.
Kitty quickly became a valuable member of the X-Men, proving her worth one Christmas Eve by single-handedly defeating one of the demonic N'Garai. Kitty formed a close friendship with both the X-Man Storm and the mutant sorceress Illyana Rasputin. The bond between Kitty and Illyana grew so strong that Kitty was eventually able to manifest the Soulsword, the ultimate expression of Illyana's magical nature.
Kitty also formed a romance with her teammate Piotr Rasputin (Colossus), and she gained a constant companion on an adventure in space in the form of a small alien dragon-like creature she named Lockheed. Kitty gained another close friend when she met Doug Ramsey, a fellow student in Stevie Hunter's dance class with whom she shared an affinity for computers. Doug's death on a mission with the New Mutants would prove to be the first of many personal losses Kitty would suffer.
After a visit to her recently divorced father, Carmen, Kitty learned that he had become involved with the Japanese Yakuza and followed him to Japan where she was captured and put under the mental control of Ogun, the martial arts master who had once been her teammate Wolverine's teacher. Using Kitty's body, Ogun attempted to kill Wolverine but failed. Wolverine then taught Kitty to become skilful enough in the martial arts to combat Ogun, and together they managed to exorcise Ogun's spirit. During the course of this adventure, Kitty took to calling herself Shadowcat.
While Colossus was away on Battleworld during what was to be called the Secret Wars, he became infatuated with an alien healer named Zsaji. Upon returning to Earth, he admitted his disloyalty to Kitty, severing their romance.
During the massacre of the underground community of mutants known as the Morlocks by the team of superhuman mutant assassins the Marauders, Kitty was injured by an energy spear hurled by the Marauder called Harpoon that adversely affected her powers. Unable to regain her solidity, Kitty was saved by the combined efforts of the European dictator Doctor Doom and his arch-rival, Reed Richards of the team of superhuman adventurers known as the Fantastic Four. However, she could now only maintain a solid form through concentration.
After witnessing the apparent death of the X-Men, Kitty helped form the British-based super-team Excalibur. During an inter-dimensional adventure, Kitty became separated from her teammates and, returning to her own Earth, she decided to give up the life of a costumed adventurer and attend college. However, unaccustomed as she was to the British educational system, Kitty was forced to enroll in St. Searle’s School for Girls. After helping save the school from closure, Kitty rejoined her recently returned teammates.
Months later, Kitty learned that Illyana was dying from the deadly mutant-killing Legacy Virus, a disease that targeted mutants. Kitty was present when Illyana finally succumbed to the disease, unaware that the young mutant's death bonded the Soulsword to her. Eventually the arcane magic's of the sword began to corrupt Kitty, and she surrendered the weapon to her then teammate Daytripper who in turn gave it to her mother, the gypsy sorceress Margali Szardos.
Soon after, Excalibur was approached by the clandestine organization known as Black Air for assistance on a mission to the island nation of Genosha. They were assigned a liaison in Pete Wisdom, an uncouth British mutant who regularly clashed with the outspoken Kitty. The pair eventually overcame their initial impressions of one another and fell in love. Wisdom even resigned from Black Air and joined Excalibur to be with Kitty.
Later, Kitty was recruited by the international law enforcement agency S.H.I.E.L.D. to repair the computer system of their flying headquarters. Kitty discovered the problem was due to Ogun’s spirit having infiltrated the computer system, and with the aid of Wolverine, she managed to purge Ogun's presence. During this time, Kitty was attracted to a S.H.I.E.L.D. intern her own age, and this made her begin to doubt her relationship with Wisdom. Soon after, she broke off their relationship.
Kitty remained a member of Excalibur until it disbanded whereupon she rejoined the X-Men. Soon after, an incident in Genosha caused Kitty to develop a rebellious attitude, reflected by her cutting her hair short, her more ferocious combat technique, and her taking to wielding one of Wolverine's broken bone claws in battle.
When Colossus sacrificed his life to release a cure for the Legacy Virus, his body was supposedly cremated, and Kitty scattered the ashes over his Russian farmland home. Mourning the loss of her old friend, and trying to live a normal life, Kitty left the X-men. She enrolled in the Robert A. Heinlein School for Engineering and Astrophysics in Chicago on a full scholarship, yet chose to live off campus and began working as a bartender for her neighbor at his establishment, the Belles of Hell. Kitty found herself unable to escape the ever-prevalent prejudice of humans, and she soon clashed with members of a student anti-mutant organization named Purity. Kitty was put on probation and was forced to attend mandatory counseling. During this time, Kitty faced her most difficult loss when she learned her father was amongst those killed in an attack on Genosha.
Kitty's battle against Purity continued after the organization attempted to frame her for the sabotage of a research experiment. A student meeting was called to debate the banning of either Purity or mutants from campus, but discussions were cut short by an attack by a new breed of mutant-hunting robotic Sentinels which were destroyed by Kitty with the help of former New Mutant Karma and Genoshan exchange student Shola Inkosi.
Kitty was later abducted by the mutant-hating Reverend Stryker to help expose the technological threat of the mutant retreat known as Mount Haven and its mysterious leader, Reverend Paul. Together, Stryker and Kitty discovered that Paul was an artificial intelligence who had killed the human townspeople and used microbial machines called nanites to transform the minds of the mutant residents from organic matter into cybernetic computers linked to his central consciousness. When Storm's team of X-Men arrived to find Kitty, Paul sought to transform them as well. Stryker attempted to use Kitty's power to disrupt electronics to destroy Paul, but he failed and Paul responded by transferring his consciousness into a global network. In an effort to safeguard his kind from Paul’s threat, Stryker merged with him in an attempt to teach him about humanity, and the town of Haven was buried by a volcanic eruption.
Soon after, Kitty assisted Storm’s team against the threat of mutant predator Elias Bogan. After Bogan was defeated, Kitty accompanied the team back to the mansion and was asked to remain as a member of Cyclops’ restructured X-Men. Peter Rasputin was discovered to be alive, his body secretly been stolen and resuscitated by Ord, an alien who had learned that an Earth mutant would be responsible for destroying his world. Kitty found Peter shortly before the X-Men's final battle with Ord, after which he rejoined the X-Men. After many years apart, Kitty and Peter reignited their romance.