Thanos was born on Saturn‘s moon Titan, and is the child of Eternals Mentor and Sui-San. Thanos carries the Deviants gene, and as such shares the physical appearance of the Eternals’ cousin race. At birth, his mother was shocked by his appearance and attempted to kill him. During his school years, Thanos was a pacifist and would only play with his brother Eros (Starfox) and pets. By adolescence, Thanos had become fascinated with nihilism and death, worshipping and eventually falling in love with the physical embodiment of death, Mistress Death. As an adult, Thanos augmented his physical strength and powers through his superior scientific knowledge. He also attempted to create a new life for himself by siring many children as well as becoming a pirate. He finds no fulfillment in either, until he is visited again by Mistress Death, for whom he murders his offspring and his pirate captain.
Cosmic Cube and Infinity Gems
Wishing to impress Mistress Death, Thanos gathers an army of villainous aliens and begins a nuclear bombardment of Titan that kills millions of his race. Seeking universal power in the form of the Cosmic Cube, Thanos travels to Earth. Prior to landing, his vessel destroys a nearby car as a family witnesses his arrival. Unbeknownst to Thanos, two of the family members in the vehicle survive: the father’s spirit is preserved by the Titanian cosmic entity Kronos and is given a new form as Drax the Destroyer while the daughter is found by Thanos’ father, Mentor, and is raised to become the heroine Moondragon. Thanos eventually locates the Cube, and also attracts the attention of Mistress Death. Willing the Cube to make him omnipotent, Thanos then discards the Cube. He imprisons Kronos and taunts Kree hero Captain Marvel, who with the aid of superhero team the Avengers and ISAAC (a super-computer based on Titan), is eventually able to defeat Thanos by destroying the Cube.
Thanos later comes to the aid of Adam Warlock in a war against the Magus and his religious empire. During this alliance Thanos cultivates a plan to reunite with Mistress Death, and secretly siphons off the energies of Warlock’s Soul Gem, and combines these with the power of the other Infinity Gems to create a weapon capable of destroying a star. Warlock summons the Avengers and Captain Marvel to stop Thanos, although the plan is foiled when Thanos kills Warlock. The Titan regroups and captures the heroes, who are freed by Spider-Man and the Thing. Thanos is finally stopped by Warlock, whose spirit emerges from the Soul Gem and turns the Titan to stone. Thanos’s spirit eventually reappears to accompany a dying Captain Marvel’s soul into the realm of Death.
The Infinity saga
Thanos is eventually resurrected, and collects the Infinity Gems once again. He uses the gems to create the Infinity Gauntlet, making himself omnipotent, and erases half the living things in the universe to prove his love to Death. This act and several other acts are soon undone by Adam Warlock. Warlock reveals that Thanos has always allowed himself to be defeated because the Titan secretly knows he is not worthy of ultimate power. Thanos joins Warlock as part of the Infinity Watch and helps him to defeat first his eviland then good personas, and cure Thor of “warrior Madness”.
The events above have been dubbed the “Infinity saga.”
Thanos later recruits a team of Earth-bound super-villains and puts them under the field leadership of Geatar in a mission to capture an ancient robot containing the obscure knowledge of a universal library and extract its data. Thanos uses information from the robot to plot against and battle Tyrant, the first creation of Galactus turned destroyer.When trapped in an alternate dimension, Thanos employs the aid of the brother of Ka-Zar, Parnival Plunder and later the Hulk to escape, although both attempts are unsuccessful. Thanos is eventually freed and comes into conflict with Thor, aligning himself with Mangog in a scheme to obtain powerful mystical and cosmic talismans which will allow him to destroy all life in the universe, and during their battles Thanos decimates the planet Rigel-3.
Thanos then uses the heroes Thor and Genis-Vell (Captain Marvel’s son) against the death god Walker, who attempts to woo Mistress Death and then destroy the entity after being rejected. Thanos then devises a plan to become the All-Father of a new pantheon of gods created by himself. Thanos, however, finds himself opposed by the Avengers’ former member Mantis and her son Quoi, who apparently is destined to be the Celestial Messiah. Thanos abandons this plan after having to unite with Mistress Death to destroy the “Rot”, a cosmic aberration in deep space caused by Thanos’s incessant love for Death. Thanos also once conducted extensive research on genetics, and after studying many of the universe’s heroes and villains cloned them and gene-spliced his own DNA into the subjects. Although he later abandons the project, five clones survive, being versions of Professor X, Iron Man, Gladiator, Doctor Strange, and Galactus respectively. A sixth and unnamed version of Thanos also appears, and it is revealed the incarnations of Thanos encountered in the past by Thor and Ka-Zar were actually clones. The true Thanos – with the aid of Adam Warlock, Gamora, Pip the Troll, Spider-Man, Captain Marvel, and Dr. Strange – destroys the remaining clones.
When the ancient Egyptian pharaoh Akhenaten uses a source of cosmic power, the Heart of the Universe, to seize power in present-day Earth (killing most of Earth’s heroes in the process), Thanos uses a time-travel stratagem to defeat him. Thanos then uses the Heart of the Universe to reverse Akhenaten’s actions and was also compelled to correct a flaw in the universe. Changed by the experience, Thanos advises confidant Adam Warlock he will no longer seek universal conquest. However, Marvel’s Executive Editor Tom Brevoorthas stated on his Tumblr blog that this story is not in any way a part of official Marvel continuity.
Thanos decides to atone for the destruction of Rigel-3, and agrees to aid a colony of Rigellians in evacuating their planet before Galactus can consume it. During the course of this mission Thanos learns Galactus is collecting the Infinity Gems in an effort to end his unyielding hunger. Thanos later learns Galactus is being manipulated into releasing a multiversal threat called Hunger, which feeds on entire universes. Despite opposition from Thanos, Galactus unwittingly frees the entity, and when its intentions are revealed, the pair team up and attempt to destroy it.
En route to the Kyln, an intergalactic prison, Thanos meets Death, who for the first time speaks to the Titan. Death claims to be worth wooing, but says Thanos must offer something other than death. At the Kyln Thanos encounters Peter Quill, also known as Star-Lord, and the Shi’ar warrior Gladiator, who are both prisoners, and the Beyonder, who has been rendered amnesiac by its choice to assume a humanoid female form. Thanos battles the Beyonder, causing its mind to shut down and leaving its power trapped within a comatose physical form. Thanos then instructs the Kyln officers to keep the Beyonder on life support indefinitely in order to prevent the entity from being reborn. Thanos departs the Kyln in the company of Skreet, a chaos-mite freed from the prison. Thanos then meets the Fallen, revealed to be the true first Herald of Galactus. Thanos defeats the former Herald and places him under complete mental control. He later appears in Wisconsin attempting to charge a weapon called the Pyramatrix with the life force of everyone on Earth until he is defeated by Squirrel Girl. After the battle, Uatu the Watcher appears and confirms to Squirrel Girl that she defeated the real Thanos, not a clone or copy.