The alleged granddaughter of the Mad Titan Thanos and daughter of Luphomoid warlord Zorr, Nebula was raised by Thanos alongside her "sister" Gamora, whom Thanos openly preferred over Nebula, causing her to develop a huge hatred towards her sister.
A short time before Thanos became permanently transfixed between life and death, Nebula sent a small band of her most trusted aides to Sanctuary II to repair its hyperdrive engines and teleport the station out of the solar system. The underlings were met by Monica Rambeau, the human then known as Captain Marvel, who had been sent to investigate the possible activity. Nebula's minions warped the satellite out of the solar system with Captain Marvel aboard and rendezvoused with Nebula. She planned to conquer the Skrull Empire, which was then in chaos after the destruction of its throneworld by the planet-devourer Galactus. Not knowing how to return home, Captain Marvel pretended to go along with Nebula's scheme but helped the Skrulls evacuate the outpost world Nebula was intent on destroying.
The Avengers eventually located their missing member and allied themselves with the Skrulls to oppose her. Before the Avengers could catch up to Nebula, she annihilated both the Skrull outpost and the planet Xandar, the home planet of Firelord. Afterward, the virtually omnipotent Beyonder, who was trying to stay on the Avengers' good side, teleported Nebula and her crew out of the galaxy.
Sometime after all this, Thanos was reborn and sought to reclaim Sanctuary. When he found Nebula there, he torched her body and left her on the brink of death, where she hovered until the affair of the Infinity Gauntlet. For whatever reason, Thanos left Nebula to roam around his shrine as he battled all manner of beings to keep the Gauntlet. After Thanos defeated Eternity and left his body, Nebula claimed the Gauntlet and fully restored herself to life as she achieved omnipotence. She eventually lost the Gauntlet to Adam Warlock and was placed in the custody of Firelord and Starfox.
Later, Nebula was freed from her cell on Titan by the loyal Geatar, who found her in a catatonic state due to her brief possession of the Infinity Gauntlet. Geatar took Nebula to Doctor Mandibus, hoping he could restore her to her former mental capacity, and he subjected her to surgery, but the damage was too severe and he had to replace several of her body parts with robotic components. This worried Geatar at first, but Nebula assured him she felt better than ever.
Nebula later resurfaced as a member of the Graces, Gamora's group of female warriors. She battled Ronan the Accuser alongside Stellaris. Ronan triumphed, severely wounding her. She later fought side-by-side with the other Graces, defending their base of operations from the Annihilation Wave.
After Thanos' son Thane decided to orchestrate a plan to kill his progenitor, he enlisted the help of Nebula, Starfox, and The Champion. As part of his plan, Thane deceived them into helping him invade Terrax's warship to steal a Phoenix Egg in his possession. Upon discovering the truth, Nebula killed Thane to prevent him from opening the egg, but his death just made the egg hatch and allowed the Phoenix Force to turn him into its new host. Thane's former allies sought Thanos' help to stop Thane, and in turn, Thanos had them take him to the God Quarry so that he could acquire the power he needed to defeat his son. While working together, Nebula and Champion had a brief romantic encounter, and, following Thane's defeat, both were left behind in the God Quarry. Nebula then fell victim to the Quarry's ensnaring illusions and didn't break free until after a considerable amount of time.
When Nebula finally escaped from the God Quarry, the trio of witches that guarded it, The Coven, informed her that Thanos had met his end at the hands of Gamora, who'd created a great weapon for herself. However, they also told her where she could find a weapon that would rival Gamora's. Nebula kidnaps the dwarf Urzuul and forced him to build an axe with teleporting abilities and help her find the Naglfar Beacon. The Asgardians of the Galaxy assembled by Kid Loki attempted to obtain the Naglfar Beacon for themselves, but they arrived too late.
Nebula tested the beacon, summoning the Naglfar Armada on Netredeen and then on Chandilar. She moved to her true target, Earth. Expecting retaliation from Asgard, Nebula subdued and kidnapped Thor to use him as leverage. She also captured Kid Loki, who had tried to warn Thor about Nebula's plans. The Asgardians of the Galaxy tracked Nebula down, and Loki incapacitated her using an illusion long enough for Valkyrie to take the Naglfar Beacon from her. During the fight, Nebula's teleporting axe was damaged, and she had Urzuul repair it. The dwarf tempered with the axe, sending Nebula somewhere unpleasant when she used the axe to escape after her defeat.
She was next seen as part of the Dark Guardians, a team brought together by Starfox after Thanos' last will revealed that his resurrection would happen in the body of another. The Dark Guardians believed Gamora would be chosen as Thanos' new vessel, so the team started a hunt for her. They eventually found Gamora alongside the Guardians of the Galaxy and a battle between the two groups ensured. During the battle, Gladiator knocked out Gamora with his eye beams, giving Nebula the chance to end Gamora's life once and for all, but when she took the shot, Star-Lord jumped in front of her, taking the hit instead.
Gamora was taken by the Dark Guardians to their ship, the Lilandra IV, but, as they prepared to kill her, Hela arrived and revealed that Thanos wouldn't come back in her body, but the body of a Titan, immediately causing Thanos' consciousness to take over his brother Starfox's mind. When the Guardians made their way to the ship (with a safe and sound Star-Lord, who'd survived thanks to his armor), Nebula and the rest of the Dark Guardians were unconscious, with only Gamora being awake to tell them about Thanos's return.
Knowing the Guardians needed all the help they could get to defeat Thanos, Nebula, and the Gladiator joined them in this effort and traveled to Knowhere, where they faced the Black Order and a horde of Outriders. In the end, they were successful in preventing Thanos's return, and Nebula apologized to Gamora for trying to kill her before bidding her farewell.
