Decades ago, Gemma Sinclair was an African-American cleaning lady at Los Alamos National Laboratory. While she is pregnant, an exploding lab experiment bombards Gemma with radiation, causing her unborn child to mutate. Nekra is born an albino with vampiric features. Loathed by her parents and community, Nekra runs away into the New Mexico desert to live alone when she is fourteen years old.
She soon encounters by chance another child who has been mutated by the same explosion. Although his parents were white, he had been born dark-skinned and had developed fur and baboon-like features, for which he had named himself Mandrill. For six years they live by theft and scavenging, until they are attacked by a lynch mob that thought they were monsters. While filled with rage, Nekra discovers she is invulnerable to the mob's attacks. Slaying a few of their persecutors, the two escape and come to regard each other as if they were siblings.
The two later leave to Africa, as part of the Mandrill's ambitious scheme to overthrow multiple nations through Black Spectre, a cult of personality powered by the Mandrill's phenomenal control over women. This effort is thwarted by Shanna the She-Devil. The two eventually escape, kidnapping Shanna's father in the process, and eventually killing him.
Their next plot is of similar means, whereby they use the Mandrill's powers to raise a cult of black women to overthrow America. They are eventually defeated on the White House lawn by Daredevil, the Black Widow, and Shanna. Abandoned by Mandrill, Nekra is captured by authorities. Nekra is held captive and drugged in a S.H.I.E.L.D. hospital, until a subliminal message from Hate-Monger inadvertently gave her the rage necessary to break free. While in the New York sewers, Nekra encounters a cult of Kali, whom she persuades that Nekra herself was the reincarnation of Kali. She then moves to the West Coast where she kills and replaces Adrienne Hatros, the reclusive sponsor of an emotional research clinic where Nekra hopes to overcome her own dependency upon emotions. There she develops a drug to subdue feelings of affection, and successfully field-tests it using Spider-Woman as the target of her feelings.
Nekra falls in with the voodoo-master the Black Talon as voodoo tutor, and with the Grim Reaper as her lover. When the Grim Reaper dies in combat, Nekra is able to briefly reanimate him as a zombie, so lifelike that even the Grim Reaper does not realize he is dead. When Nekra's love becomes greater than her hate though, the Reaper dies again. Nekra takes his corpse with her, in hopes of reanimating him again.
Nekra spends some time in the super-villain prison The Vault. During a prison wide riot, she and Mister Hyde have a brief romantic interlude. Nekra finally manages to re-animate the Grim Reaper again, but this time there is a caveat: he has to kill one person every 24 hours in order to stay 'alive.' The Reaper chooses Nekra as his first victim and kills her.
Sensing the potential threat of Doctor Druid, Daimon Hellstrom uses his magics to reanimate Nekra, and sends her to investigate him. First she seduces Dr Druid, which negates his powers, but he manages to regain them via sacrifice. Nekra then shoots Dr. Druid in the forehead, killing him.
Nekra is one of a handful of mutants to have retained her powers in the wake of House of M.
Nekra is seen during the riots in San Francisco with Frenzy of the Acolytes. Both are told by Karma to behave but Nekra tells her they were promised Utopia and they will never stop hunting mutants. They'll always be hunted, tormented and killed. She is then blasted by Ms. Marvel. She later takes part in final battle; once again pitted against Osborn's Dark Avengers as well as his X-Men and follows the rest of the mutants to the island of Utopia. It is also revealed that she has a daughter named Death Reaper who is an ally of the villain Zodiac.
During the Chaos War storyline, Nekra assists a resurrected Grim Reaper in fighting the Dead Avengers. She was killed with the Grim Reaper when Vision self-destructed.
Nekra is a formidable hand to hand combatant, even without the use of any of her powers. She is also proficient in various voodoo rituals, particularly the creation and manipulation of zombies. She's developed her own unique hybrid of voodoo practices, namely combining teachings of Black Talon and the Cult of Kali.
Possesses the ability to increase her strength, endurance, and resistance to pain and injury by harnessing her violent emotions. Her heightened adrenal activity causes a series of metabolic reactions within her body that toughen her skin and increase the efficiency of her muscles. At her peak, she can lift approximately 10 tons, withstand an explosion of about 100 pounds of TNT, and withstand extreme degrees of cold and heat. Her powers are limited by how long she can sustain her emotional state, generally for no more than an hour. Nekra is also formidable in hand to hand combatant, even without the use of any of her powers.