The Thanos Imperative is a six-issue comic book mini-series written by Dan Abnett and Andy Lanning which was published by Marvel Comics. The mini-series was bookended by two one-shot comics, Thanos Imperative: Ignition and Thanos Imperative: Devastation. It follows up the events of the crossover story "Realm of Kings" which introduced the Cancerverse and the "War of Kings" crossover event before it. Which involved an intergalactic war that resulted in the creation of a tear in the fabric of the universe, creating "The Fault" in the void between the Milky Way galaxy, the Andromeda galaxy, and the Shi'ar galaxy.
Concerned about the Fault, several groups take action to investigate the phenomena. The Nova Corps and Guardians of the Galaxy, send Quasar into the Fault. Who discovers a corrupted universe ruled by evil colossal organic entities. He is captured by the Revengers, corrupted versions of the Avengers and is informed by their leader Lord Mar-Vell of their plan to extend the rule of their gods, the Many-Angled Ones to his reality (Earth-616). Meanwhile the million-world Shi'ar empire send a unit of its super-powered Imperial Shi'ar Guard to investigate the Fault. In the process they encounter insectoid refugees from that reality who they are forced to battle and afterwards encounter living bio-ships carrying abominations and the Ex-Men (mutated X-Men). Losing several team members in the process before they manage to escape and warn the Shi'ar and Kree empires of the coming threat.
Erupting from the Fault is an invasion of colossal starships (many of them with giant head or skull-like bows) and eldritch monsters. Which tear through the forces assembled to stop the invasion. Opposing the invaders was a massive fleet of starships from the Kree and Shi'ar empires, the Rigellian colonists, and the Negative Zone Horde among others. Assisting them were the Galadorian Spaceknights and the Nova Corps. Soon they were joined by Galactus the Devourer of Worlds, several Cosmic Heralds (including the Silver Surfer), and a good number of cosmic aspects (including Celestials). Despite the impressive force assembled, they were taking massive casualties, as they were being overwhelmed. Chthonic entities were able to tear through the starships and even kill cosmic aspects. The invaders brought through the Fault, the Galactus Engine, an Eldritch weapon of mass destruction, and various cosmic aspects fell to the weapon. Soon the Negative Zone Horde withdrew from the battle, abandoning their allies and due to the losses the defenders were suffering they were forced to retreat. The invaders in turn were searching for the universe's Avatar of Death (Thanos) to kill so that this reality's Death would cease to exist.
In the meantime, the Guardians of the Galaxy, Nova (Richard Rider), and Thanos the Mad Titan went into the Fault and crossed over into the Cancerverse. They were going to attempt to cripple the invasion from the other side and if possible close the Fault. Upon arriving on the other side, Drax the Destroyer was overwhelmed by the power of Life in that reality that he became an Avatar of Life and killed Thanos. Who soon resurrected back to life as death was non-existent in that reality. Soon they encountered the Defenders of the Realm (the corrupted Defenders) who they managed to hold off and escape with the assistance of the Scarlet Witch. She had fooled the Revengers into thinking she was one of them, having protected herself with layers of hexes and was actually working undercover for the Machine Resistance led by Vision. In the Cancerverse, the only ones who were not under the control of the Many-Angled Ones were the sentient machines. Soon the Revengers tracked them down to the resistance base and they fought each other, until Thanos appeared to defect to their side, in exchange for being permanently killed. Which Lord Mar-Vell did in a ritual, only to discover he had been tricked as doing so brought Earth-616's cosmic aspect of Death into the Cancerverse. Lord Mar-Vell was then killed and the universe crippled, the invasion stopped. Nova and Star-Lord stayed behind to keep Thanos within the Cancerverse, fighting him and giving their teammates time to escape back to their home reality. They were going to sacrifice themselves so that Thanos would never threaten their own universe as he died along with everything else in the Cancerverse which was being destroyed.
The Negative Zone warlord Blastaar led his Negative Zone Horde against the greatly weakened Kree Empire which had not yet recovered from the Cancerverse invasion, and the previous Shi'ar-Kree war. They were on the verge of conquering the Kree throneworld of Hala, when several cosmic heroes led by the Silver Surfer arrived to the aid of the Kree. Forcing them to withdraw after which the heroes formed a new cosmic troubleshooting team, the Annihilators. It was later discovered that Star-Lord, Nova, and Thanos had all made it back to their home reality and that the Cancerverse was not destroyed. As Death returned to it's home reality, the Cancerverse was able to recover and was regaining its strength.